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National Water-Quality Assessment Program Water-Quality Assessment of Part of the Upper Mississippi River Basin, Minnesota and Wisconsin Ground-Water Quality in the Prairie du Chien-Jordan Aquifer, 1996
Water-Resources Investigations Report 98-4248
Upper Mississippi River Basin
National Water-Quality Assessment Study Unit
U.S. Department of the Interior U.S. Geological Survey
United States Department of the Interior
U.S. GEOLOGICAL SURVEY Water Resources Division 2280 Woodale Drive Mounds View MN 55112 (612) 783-3230 email: [email protected]
February 26, 1999
Dear Colleague,
Enclosed find our most recent report written as part of the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program in the Upper Mississippi River Basin (UMIS), entitled "Water-Quality Assessment of Part of the Upper Mississippi River Basin, Minnesota and Wisconsin Ground- Water Quality in the Prairie du Chien-Jordan Aquifer, 1996," by Alison L. Fong, William J. Andrews, and James R. Stark. This report describes chemical charac teristics of water in the Prairie du Chien-Jordan aquifer, the principal aquifer in terms of source water to wells in the Twin Cities metropolitan area, and the effects of confining units on the qual ity of the water. Additional copies of the report, released as Water-Resources Investigations Report 98-4248, can be purchased from the U.S. Geological Survey, Branch of Information Ser vices, Box 25286, Federal Center, Denver CO 80225-0286.
Sincerely,
James R. Stark Study Chief, UMIS NAWQA
Enclosure
U.S. Department of the Interior U.S. Geological Survey
Water-Quality Assessment of Part of the Upper Mississippi River Basin, Minnesota and Wisconsin Ground-Water Quality in the Prairie du Chien-Jordan Aquifer, 1996
By Alison L. Fong, William J. Andrews, and James R. Stark
Water-Resources Investigations Report 98-4248
National Water-Quality Assessment Program U.S. Department of the Interior Bruce Babbitt, Secretary
U.S. Geological Survey Charles G. Groat, Director
Use of product names is for descriptive purposes only and does not constitute endorsement by the U.S. Geological Survey
Mounds View, Minnesota, 1998
For additional information write to: District Chief U.S. Geological Survey, WRD 2280 Woodale Drive Mounds View MN 55112
Copies of this report can be purchased from: U.S. Geological Survey Branch of Information Services Box 25286 Federal Center Denver CO 80225
Information regarding the National Water-Quality Assessment Program (NAWQA) is available on the Internet via the World Wide Web. You may connect to the NAWQA Home Page using the Universal Resource Locator (URL) at: http://wwwrvares.er.usgs.gov/nawqa/nawqa_home.html
Information about the Upper Mississippi River Basin Project of the NAWQA Program is available on the World Wide Web at: http://wwwmn.cr.usgs.gov/umis/index.html
Water-Resources Investigations Report 98-4248 Forward Improve understanding of the primary natural and human factors that affect water-quality The mission of the U.S. Geological Survey conditions. (USGS) is to assess the quantity and quality of the This information will help support the earth resources of the Nation and to provide development and evaluation of management, information that will assist resource managers and regulatory, and monitoring decisions by other Federal, policy makers at Federal, State, and local levels in State, and local agencies to protect, use, and enhance making sound decisions. Assessment of water-quality water resources. conditions and trends is an important part of this overall mission. The goals of the NAWQA Program are being achieved through ongoing and proposed investigations One of the greatest challenges faced by water- of 60 of the Nation's most important river basins and resources scientists is acquiring reliable information aquifer systems, which are referred to as study units. that will guide the use and protection of the Nation's These study units are distributed throughout the Nation water resources. That challenge is being addressed by and cover a diversity of hydrogeologic settings. More Federal, State, interstate, and local water-resource than two-thirds of the Nation's freshwater use occurs agencies and by many academic institutions. These within the 60 study units and more than two-thirds of organizations are collecting water-quality data for a the people served by public water-supply systems live host of purposes that include: compliance with permits within their boundaries. and water-supply standards; development of remediation plans for a specific contamination National synthesis of data analysis, based on problem; operational decisions on industrial, aggregation of comparable information obtained from wastewater, or water-supply facilities; and research on the study units, is a major component of the program. factors that affect water quality. An additional need for This effort focuses on selected water-quality topics water-quality information is to provide a basis on using nationally consistent information. Comparative which regional and national-level policy decisions can studies will explain differences and similarities in be based. Wise decisions must be based on sound observed water-quality conditions among study areas information. As a society we need to know whether and will identify changes and trends and their causes. certain types of water-quality problems are isolated or The first topics addressed by the national synthesis are ubiquitous, whether there are significant differences in pesticides, nutrients, volatile organic compounds, and conditions among regions, whether the conditions are aquatic biology. Discussions on these and other water- changing over time, and why these conditions change quality topics will be published in periodic summaries from place to place and over time. The information can of the quality of the Nation's ground and surface water be used to help determine the efficacy of existing as the information becomes available. water-quality policies and to help analysts determine This report is an element of the comprehensive the need for and likely consequences of new policies. body of information developed as part of the NAWQA To address these needs, the Congress appropriated Program. The program depends heavily on the advice, funds in 1986 for the USGS to begin a pilot program in cooperation, and information from many Federal, seven project areas to develop and refine the National State, interstate, Tribal, and local agencies and the Water-Quality Assessment (NAWQA) Program. In public. The assistance and suggestions of all are greatly 1991, the USGS began full implementation of the appreciated. program. The NAWQA Program builds upon an Robert M. Hirsch existing base of water-quality studies of the USGS, as Chief Hydrologist well as those of other Federal, State, and local agencies. The objectives of the NAWQA Program are to: Describe current water-quality conditions for a large part of the Nation's freshwater streams, rivers, and aquifers. Describe how water quality is changing over time.
in IV Contents Page Abstract...... ^ Introduction ...... Purpose and scope...... ^ Description of the study area ...... 2 Climate...... ^ Hydrogeologic setting...... ^ Land use and land cover...... ? Population and water use...... 7 Methods of well selection, sample collection, and data analysis...... ? Acknowledgments...... ^ Ground-water quality...... ^ Physical parameters...... ^ Major ions ...... Nutrients and dissolved organic carbon...... 14 Trace metals...... ^ Radon ...... Tritium ...... ^ Pesticides...... ^ Volatile organic compounds ...... 23 Implications of water-quality variability between confined and unconfmed portions of the Prairie du Chien-Jordan aquifer ...... 26 Water-quality variability between the Prairie du Chien Group and the Jordan Sandstone portions of the Prairie du Chien-Jordan Aquifer...... ^ Summary and conclusions...... ^ References ...... Supplemental information...... ^ Illustrations Figures 1-3. Maps showing: 1. Location of the Upper Mississippi River study unit, Prairie du Chien-Jordan aquifer study area, and estimated extent of the confined and unconfined areas...... 3 2. Surficial hydrogeology in the Prairie du Chien-Jordan aquifer study area ...... 4 3. Bedrock hydrogeology in the Prairie du Chien-Jordan aquifer study area ...... 5 4. Generalized hydrogeologic column showing aquifers and confining units in the study area...... 6 5. Map showing land use and land cover in the Prairie du Chien-Jordan aquifer study area ...... 8 6-7. Boxplots showing: 6. Field measurements of physical parameters in water samples from Prairie du Chien-Jordan aquifer study area wells...... ^ 7. Concentrations of dissolved major ions in water samples from Prairie du Chien-Jordan aquifer study area wells...... 8. Piper diagrams showing major ion composition of water samples from Prairie du Chien-Jordan aquifer study area wells...... 13 Illustrations-continued 9. Boxplots showing concentrations of dissolved nutrients and dissolved organic carbon in water samples from Prairie du Chien-Jordan aquifer study area wells...... 15 10. Map showing locations of wells and nitrate concentrations in water samples from wells completed in the Prairie du Chien-Jordan aquifer...... ^ 11-12. Boxplots showing: 11. Concentrations of trace metals in water samples from Prairie du Chien-Jordan aquifer study area wells...... 17 12. Concentrations of radon in water samples from Prairie du Chien-Jordan aquifer study area wells...... 18 13. Map showing locations of wells and radon concentrations in water samples from wells completed in the Prairie du Chien-Jordan aquifer...... 19 14. Boxplots showing concentrations of tritium in water samples from Prairie du Chien-Jordan aquifer study area wells .....20 15. Map showing locations of wells and tritium concentrations in water samples from wells completed in the Prairie du Chien-Jordan aquifer ...... 21 16. Map showing locations of Prairie du Chien-Jordan aquifer study area wells with water samples having detectable concentrations of pesticide compounds...... 22 17. Barchart showing frequencies of detection of pesticide compounds in water samples from Prairie du Chien-Jordan aquifer study area wells...... ^ 18. Map showing locations of Prairie du Chien-Jordan aquifer study area wells with water samples having detectable concentrations of volatile organic compounds...... 24 19. Barchart showing frequencies of detection of volatile organic compounds in water samples from Prairie du Chien-Jordan aquifer study area wells...... 25 Tables 1. Medians, standard deviations, and ranges in well characteristics and values of physical parameters in water samples from Prairie du Chien-Jordan study area wells...... 34 2. Laboratory analysis methods for measured water-quality constituents ...... 34 3. Reporting limits and concentrations of analytes in blanks...... 35 4. Reporting limits and percent recoveries for Schedule 2010 pesticide spikes ...... 36 5. Reporting limits and percent recoveries for custom method 9090 volatile organic compound spikes...... 3 8 6. Reporting limits and concentrations of compounds with greater than five percent differences in concentrations in replicate samples ...... ^ 7. Medians, standard deviations, and ranges in values of concentrations of major ions dissolved in water samples from Prairie du Chien-Jordan study area wells...... 40 8. Number of samples with detectable concentrations, reporting limits, median values, standard deviations, and ranges in concentrations of nutrients and dissolved organic carbon in water samples from wells in the unconfined and confined portions of the Prairie du Chien-Jordan study area ...... 40 9. Number of samples with detectable concentrations, reporting limits, median values, standard deviations, ranges in concentrations, and maximum contaminant levels of trace metals in water samples from wells in the unconfined and confined portions of the Prairie du Chien-Jordan study area...... 41 10. Pesticide compounds analyzed in water samples, by chemical class...... 42 11. Reporting limits, number of samples with detectable concentrations, ranges in concentrations, and maximum contaminant levels of pesticide compounds in water samples from Prairie du Chien-Jordan study area wells ...... 43 12. Volatile organic compounds analyzed in water samples, by chemical class...... 44 13. Reporting limits, number of samples with detectable concentrations, ranges in concentrations, and maximum contaminant levels of volatile organic compounds detected in water samples from Prairie du Chien-Jordan study area wells ...... 45
VI Conversion Factors, Abbreviated Water-Quality Units, and Abbreviations Multiply By To obtain inch (in.) 25.4 millimeter foot (ft) 0.3048 meter square mile (mi2) 2.590 square kilometer gallon 3.785 liter million gallons per day (mgal/d) 3.785 million liters per day degrees Fahrenheit (°F) (temperature °F - 32)/1.8 degrees Celsius
Chemical concentrations of substances in water are given in metric units of milligrams per liter (mg/L) and micrograms per liter (|ig/L). Milligrams per liter is a unit expressing the concentration of chemical constituents in solution as mass (milligrams) of solute per unit volume (liter) of water. Micrograms per liter is a unit expressing the concentration of chemical constituents in solution as mass (micrograms) of solute per unit volume (liter) of water.
Abbreviations used in this report: ATSDR Agency for Toxic Substances and Disease Registry, an agency of the U.S. Department of Health and Human Services Dl Deionized water DOC Dissolved organic carbon CIS Geographic Information System GWSI Ground-Water Site Inventory JDN Jordan MCL Maximum Contaminant Level, a health-based water-quality standard set by the USEPA MPCA Minnesota Pollution Control Agency NADP/NTN National Acidic Deposition Program/National Trends Network NAWQA National Water-Quality Assessment ATO Nephelometric Turbidity Units PDCJ Prairie du Chien-Jordan PDC Prairie du Chien QA/QC Quality-assurance/quality-control SI Saturation indices SMCL Secondary maximum contaminant level, an unenforceable guideline regarding taste, odor, color, and certain other non-aesthetic effects of drinking water set by the USEPA TCMA Twin Cities metropolitan area UMIS Upper Mississippi River Basin study unit USEPA U.S. Environmental Protection Agency USGS U. S. Geological Survey VOC Volatile organic compound
vn Water-Quality Assessment of Part of the Upper Mississippi River Basin, Minnesota and Wisconsin Ground-Water Quality in the Prairie du Chien-Jordan Aquifer, 1996
By Alison L Fong, William J. Andrews, and James R. Stark
Abstract In the confined portion of the aquifer no samples exceeded the maximum contaminant level of 10 milligrams per liter for The Prairie du Chien-Jordan (PDCJ) aquifer (Prairie du nitrate. In the unconfined portion of the aquifer nitrate in two Chien-Trempealeau aquifer in Wisconsin), composed of dolo samples exceeded the maximum contaminant level of 10 milli mite and sandstone of Cambrian to Ordovician age, is the grams per liter. Phosphorus concentrations were generally about principal bedrock aquifer in the Upper Mississippi River study an order of magnitude less than nitrate concentrations. unit of the National Water-Quality Assessment (NAWQA) Pro Iron and manganese concentrations commonly exceeded the gram. The aquifer supplies approximately 75 percent of the secondary maximum contaminant levels set by the U.S. Environ ground water withdrawn in the area. In certain areas, the aquifer mental Protection Agency and were generally greater in the is overlain by bedrock or glacial deposits having low hydraulic confined portion of the PDCJ aquifer, although the differences conductivity (termed "confined portion" of the aquifer in this were not statistically significant at the 95 percent confidence report). In other areas the aquifer is overlain by glacial sand and level (nonparametric Mann-Whitney test). Radon concentrations gravel deposits having greater hydraulic conductivity (termed were greater in the confined portion of the aquifer than in the "unconfined portion" of the aquifer in this report). Differences in unconfined portion, although the difference was not statistically the hydrogeologic characteristics of these overlying units have significant at the 95 percent confidence level (two sample t-test), potential to affect the downward movement of water and of con with medians of 500 and 340 picoCuries per liter, respectively. taminants into the aquifer from the land surface. Sixty-six percent of the radon concentrations were greater than Ground-water samples were collected from 50 domestic the suspended maximum contaminant level of 300 picoCuries wells completed in this aquifer in July, August, and September per liter. Tritium concentrations indicate that water in the uncon of 1996 as part of the U.S. Geological Survey's National Water- fined portion of the PDCJ aquifer may have been recharged Quality Assessment Program. The purpose of this report is to more recently than water in the confined portion of the aquifer, describe the chemical characteristics of water in the PDCJ aqui although differences in tritium concentrations between confined fer and to summarize the differences in water quality in confined and unconfined portions of the aquifer were not statistically sig and unconfined portions of the aquifer. Twenty-five wells were nificant at the 95 percent confidence level (nonparametric Mann- sampled in each portion of the aquifer. Water samples from the Whitney test). Atrazine and its metabolite, deethylatrazine, were wells were measured for physical parameters and analyzed for the most frequently detected pesticide compounds in water sam concentrations of major ions, nutrients, dissolved organic car ples from the PDCJ aquifer. Volatile organic compounds were bon, trace metals, radon, tritium, pesticides, and volatile organic detected in 41 of the 50 water samples, but none of the concen compounds. trations exceeded 1 microgram per liter. Concentrations of Differences in anthropogenic and naturally occurring materi volatile organic compounds were slightly greater in the uncon als in water between confined and unconfined portions of the fined portion, although the differences in detection rates were PDCJ aquifer are small and frequently the differences are not not statistically significant at the 95 percent confidence level statistically significant at the 95 percent confidence level. Dis (nonparametric Mann-Whitney test). Carbon disulfide and solved oxygen concentrations were slightly less and specific methyl chloride were the most frequently detected volatile conductances and alkalinities were slightly greater in water in organic compounds. the confined portion of the aquifer. Only the differences in spe Water in the unconfined portion of the PDCJ aquifer in Min cific conductance and alkalinity, however, were statistically nesota and Wisconsin appears to be affected to a greater degree significant at the 95 percent confidence level (two sample t-test). by anthropogenic activities than water in the confined portion of Concentrations of most major ions were generally greater in the aquifer. Water in the confined portion has a longer residence water from the confined portion of the aquifer. time and greater concentrations of dissolution products of miner Nitrate (nitrite plus nitrate as N) and phosphorus were gener als. In general, however, differences in anthropogenic and ally greater in the unconfined portion of the PDCJ aquifer naturally occurring materials among confined and unconfined although the differences were not statistically significant at the portions of the aquifer are small and frequently not significantly 95 percent confidence level (nonparametric Mann-Whitney test). different. Introduction the ground water withdrawn in the area Climate (Stark and others, 1996; Metropolitan Seasonal fluctuations in temperature In 1991, the USGS began full imple Council, 1992). and rainfall can affect the solubility of mentation of the NAWQA program. The VOCs in rainfall, volatilization of VOCs long-term goals of NAWQA are to Purpose and Scope to the atmosphere, seasonal loadings of describe the status of and trends in the pesticides in rainfall, relative amounts of quality of large representative parts of the The purpose of this report is to runoff and infiltration, and processes Nation's surface- and ground-water describe the chemical characteristics and the effects of confinement of water in the such as mineral dissolution and precipita resources and to identify the major natu tion, sorption, and denitrification, which ral and anthropogenic factors that affect PDCJ aquifer in the UMIS study unit. The study area (fig. 1), as defined for this can affect the quality of ground water. the quality of these resources. To meet Average monthly temperatures in the these goals, nationally consistent data report, consists of the part of the UMIS study area range from about 10 °F in Jan useful to policy makers, scientists and study unit underlain by the PDCJ aquifer uary to greater than 70 °F in July managers are being collected and ana in areas where the aquifer is an impor tant source of water to domestic, (Minnesota State Climatologist, elec lyzed. Because assessment of the water tronic commun., 1995). Average annual quality in the entire Nation is impracti commercial, industrial, and irrigation precipitation is between 29 and 32 in. cal, major activities of NAWQA take wells. Fifty domestic wells completed in (Minnesota State Climatologist, elec place within a set of hydrologic systems the aquifer were sampled during July, August, and September of 1996 25 in tronic commun., 1995). About three- called study units. Study units comprise fourths of the annual precipitation falls diverse hydrologic systems of river portions of the aquifer overlain by con from May through September (Baker and basins, aquifer systems, or both. fining units consisting of bedrock or glacial deposits (termed "confined por others, 1979). Mean annual free-water The UMIS study unit (fig. 1), which tion" of the aquifer in this report) and 25 surface evaporation ranges from 34 to 36 encompasses an area of about 47,000 . in. (Farnsworth and others, 1982). r\ in portions of the aquifer that are not mi , includes the entire drainage area of overlain by confining units (termed Hydrogeologic Setting the Upper Mississippi River Basin from "unconfined portion" of the aquifer in the headwaters to the outlet of Lake this report) (fig. 1). Water samples were The presence and concentrations of Pepin. The UMIS study unit includes analyzed for nearly 200 water-quality many constituents in ground water are areas of agricultural lands, forests, wet constituents, including physical parame affected by the hydraulic conductivity and lands, prairies, and a major urban area ters, major ions, nutrients, DOC, trace chemical composition of overlying uncon- the TCMA (with a population of approxi metals, radon, tritium (in selected sam solidated deposits and bedrock units. Soils mately 2,300,000) (Stark and others, ples), pesticides, and VOCs. Water- in the study area include light, well-drained 1996). Water quality of the Upper Missis quality samples from the wells were used psamments, alfisols, and poorly-drained sippi River Basin, which includes the to evaluate the quality of water in the histosols (Stark and others, 1996). Beneath headwaters of the largest river system in aquifer and the influence of overlying the soils, the study area is mantled with the Nation, is of concern due to reliance confining units. Differences in water less than 50 to greater than 450 ft of gla on surface water by major municipalities quality between portions of the aquifer cial and alluvial deposits (fig. 2) including in the basin and due to the necessity of overlain, and not overlain, by confining sand and gravel (glacial outwash and allu good quality water to maintain the health units are summarized in this report. In vium), and glacial tills deposited primarily of aquatic ecosystems. Ground water is addition, a comparison of water quality by the Des Moines Lobe (in the west) and the principal source of potable water to between the Prairie du Chien (PDC) by the Superior Lobe (in the northeast) smaller municipalities and domestic Group and the Jordan (JDN) Sandstone (Norvitch and others, 1973; Bloomgren water systems in the study unit. Ground (stratigraphic units containing the aqui and others, 1989; Meyer and Hobbs, 1989; water in sand and gravel aquifers of gla fer) is presented. Schoenberg, 1990). Unconsolidated cial and alluvial origins and in near- deposits in the study area are underlain surface bedrock aquifers is particularly Description of the Study Area by up to 1,000 ft of sedimentary strata (fig. susceptible to degradation from anthropo 3) ranging in age from Precambrian to genic activities. The presence and distribution of the Devonian. Sedimentary units in the study Activities during the first phase of analyzed constituents in ground water can area are underlain by so-called "base NAWQA for this study unit (1994-99) be affected by the environmental setting ment" units of metamorphic and igneous are focused principally on the effects of of the study area. Major variables that rocks of Precambrian age. Underlying the the TCMA on water quality and aquatic can influence ground-water quality TCMA, bedrock units fill a concave ecosystems. The Prairie du Chien-Jordan include climate, hydrogeologic setting, depression known as the Twin Cities (PDCJ) aquifer is the primary source of land use and land cover, population and Basin. The terms for rock units and ground water for domestic wells and pub water use. These variables are described hydrogeologic units in the study area lic water supplies in the TCMA, for the study unit in Stark and others vary slightly between Minnesota and supplying approximately 75 percent of (1996). Wisconsin (fig. 4). In addition, there are 93°45' 93030' 93°15' 93°00' 92°45' 92°30' 92° 15'
44=30' -
Twin Cities , metropolitan area (TCMA) r-Lake Pepin 45°15' - ANOKA - ^j The Upper Mississippi River Basin study unit
45°00'
[Lake Minrketonka CARVER
44045. _
44°30'
44°15' - EXPLANATION Estimated extent of the confined Prairie du Chien-Jordan aquifer Estimated extent of the unconfined 25 Miles I I Prairie du Chien-Jordan aquifer I i I I | Boundary of study area 44°00' 25 Kilometers Boundary of the Upper Mississippi River Basin study unit Base from U.S. Geological Survey digital data 1:100,000, 1990, Albers Equal-Area Conic Boundary of the Twin Cities projection. Standard parallels: 29°30' and 45°30', metropolitan area (TCMA) central meridian: -93°00' Well completed in the confined aquifer Extent of the confined and unconfined Prairie du Chien- Well completed in the Jordan aquifer used in this study was modified from Brown, 1988; Kanivetsky, 1978; Mudrey and others, unconfined aquifer 1987; Olcott,1992. Figure 1.-Location of the Upper Mississippi River Basin study unit, Prairie du Chien-Jordan aquifer study area, and estimated extent of the confined and unconfined areas. 93°45' 93°30' 93°15' 93°00' 92°45' 92°30' 92°15'
44°30'
45°15' -
The Upper Mississippi River Basin study unit
45°00' -
44045. _
44°30'
Surficial hydrogeology modified from Olcott,1992. 44° 15' -
EXPLANATION
Glacial outwash, coarse-grained glacial-lake sediment or coarse- and fine-grained alluvium of calcareous and siliceous deposits 44°00' - Glacial till of calcareous or Base from U.S. Geological Survey digital data siliceous deposits 1:100,000, 1990, Albers Equal-Area Conic projection. Standard parallels: 29°30' and 45°30', Boundary of study area central meridian: -93°00' Boundary of Upper Mississippi River Basin study unit
Figure 2.--Surficial hydrogeology in the Prairie du Chien-Jordan aquifer study area 93045. 93°30' 93°15' 92°45'_____92°30' 92°15'
44°30'
45°15'
The Upper Mississippi River Basin study unit
45°00' -
44045
44°30'
44°15' r. Bedrock hydrogeology modified from Brown,1988; Kanivetsky, 1978; Mudrey and others, 1987.
Base from U.S. Geological Survey digital data 1:100,000, 1990, Albers Equal-Area Conic projection. Standard parallels: 29°30' and 45°30', central meridian: -93°00'
EXPLANATION 44°00' DESCRIPTION OF AQUIFERS: Based upon State of Minnesota classification and terminology
CEDAR VALLEY-MAQUOKETA-GALENA ^^^ MT. SIMON-HINCKLEY-FOND DU LAC
PRECAMBRIAN IGNEOUS AND METAMORPHIC ROCKS PRAIRIE DU CHIEN-JORDAN (in Minnesota); r PRAIRIE DU CHIEN-TREMPEALEAU (in Wisconsin) |UNKNOWN £ FRANCONIA-IRONTON-GALESVILLE (in - Faults, dashed where approximated Minnesota); TUNNEL CITY-WONEWOC- Boundary of study area EAU CLAIRE (in Wisconsin) Boundary of the Upper Mississippi River Basin study unit Figure 3.-Bedrock hydrogeology in the Prairie du Chien-Jordan aquifer study area. minor differences in the ways in which to be unconfined where these units are Methods of Well Selection, Sample rock units and hydrogeologic units are absent. Collection, and Data Analysis grouped within a given term. In this report, terms commonly used in Minne Land Use and Land Cover The 50 sampled domestic wells were sota are used. The PDCJ aquifer consists selected by using a CIS-based random, Land use and land cover in the study of up to 335 ft of fractured sandy dolomite equal-area algorithm (Scott, 1990). For area consists primarily of agricultural of the PDC Group of Ordovician age, and the Minnesota portion of the study area, lands, forests, and urban areas (fig. 5). the underlying quartz sandstone of the JDN the County Well-Index database of the Land use and land cover can influence Sandstone of Cambrian age (fig. 4). The Minnesota Geological Survey and the PDC is karstic, with ground-water flow the presence and distribution of constitu Ground-Water Site Inventory (GWSI) occurring mainly through joints, fractures, ents in ground water (Stark and others, database of the USGS were used to com and solution cavities, whereas flow in the 1996). Agricultural land uses can be pile a list of suitable wells, from which JDN is primarily through the intergranular sources of nutrients and pesticides to primary and alternate wells were selected pore spaces and some joint partings (Delin ground water. Urban and suburban land for confined and unconfined portions of and Woodward, 1984). The PDC and the uses contribute nitrogen and phosphorus the aquifer. For the Wisconsin portion of JDN are in effective hydraulic connection to ground water through leaching of fer the study area, relatively few suitable and have traditionally been considered a tilizers applied to residential lawns and to wells were listed in GWSI. Instead, suit single aquifer (Delin and Woodward, parks and golf courses. Landfills and able wells near randomly selected 1984; Young, 1992a; Young, 1992b). On a waste sites can also contribute contami sampling locations were identified from regional scale they have similar hydraulic nants to ground water. Roadways and well logs supplied by the Wisconsin heads and water-level fluctuations; how railroads can be sources of chloride from Department of Natural Resources. Wells ever, the lower part of the PDC may serve applications of salt for de-icing, of herbi were selected based on lithologic infor locally as a partial confining unit (Setter- cides applied in their rights-of-way, and mation provided on the well logs and not holm and others, 1991) for the JDN. On a of VOCs emitted to the air or spilled on based on the generalized stratigraphic local basis, aquifer heterogeneity can cre their surfaces. Chemicals used by home- information shown on figure 1. Conse ate vertical hydraulic-head differences owners can also be sources of VOCs to quently, wells designated as being between the two stratigraphic units. These ground water. Commercial and industrial completed in confined and unconfined differences, combined with differences in establishments may also discharge VOCs portions of the aquifer do not precisely the mineralogy and petrology between the and other substances to the atmosphere or match the information provided on fig two units, can result in small differences in to the land surface. The most concen ure 1. the quality of water between the units. trated area of potential contaminant Physical parameters measured during sources in the study area is the TCMA. The PDCJ aquifer is overlain by sampling included depth to water, water younger bedrock units or by unconsoli- temperature, pH, specific conductance, Population and Water Use dated sands or tills of varying thicknesses dissolved oxygen, turbidity, and alkalin throughout its extent (figs. 2, 3 and 4). The estimated population of the study ity (table 1, in the Supplemental Although the sequence of glaciation in area in 1994 was about 3.2 million peo Information section). Water samples were the study area is complex, glacial depos ple (Missouri State Census Data Center, collected in sealed systems utilizing its in the western portion tend to be Teflon tubing and stainless steel fittings, U.S. Bureau of the Census data, elec associated with the Des Moines Lobe and according to NAWQA protocols (Kot- tronic commun., 1997). Approximately are more clay-rich than glacial deposits in erba and others, 1995). The wells were 75 percent of the population resides in the the eastern portion of the study area, purged by pumping three to five stand which are associated with the Superior TCMA (U.S. Bureau of the Census, ing volumes of water from the wells Lobe. The aquifer is generally closer to 1991). In 1990, throughout the TCMA, using the existing pumping systems. The land surface in the eastern portion of the an average of 324 million gallons of stability of water chemistries were veri study unit where glacial till confining ground water per day were used. The fied through periodic measurements of units are less extensive. The aquifer is PDCJ aquifer is the principal source of physical parameters made while purging incised in many areas by alluvium and water for public-supply wells in subur the wells. Water samples to be analyzed glacial-outwash-filled valleys (Schoen- ban communities surrounding the Twin for major ions, nutrients, DOC, trace met berg, 1990). The lower part of the Cities, supplying approximately 75 per als, radon, tritium, pesticides, and VOCs overlying St. Peter Sandstone, where it cent of the ground water withdrawn (243 were shipped to the USGS National exists, is considered a confining unit in mgal/d) in the TCMA in 1990 (Andrews Water-Quality Laboratory in Arvada, the study area (Olcott, 1992). For this and others, 1995a; Metropolitan Council, Colorado where analyses were done report, the PDCJ is considered to be con 1992). The PDCJ aquifer is also the pri according to USGS analytical protocols fined where it is overlain by younger mary source of water for domestic wells for analysis, quality assurance, and qual bedrock units or by at least 10 ft of clay inside and outside of the TCMA in the ity control (table 2, in the Supplemental or clay-rich glacial till and is considered study area. Information section). 93°45' 93°30' 93°15' 93°00' 92°45' 92°30' 92°15'
44030'
45°15'
The Upper Mississippi River Basin study unit '' * '.; /
45°00' -
44°45' ~
44030'
44°15' Land use and land cover data from Hitt, 1994
EXPLANATION Land use and land cover:
0 25 Miles Agriculture Wetland I I I 1 _l I I 1 1 1 Urban Water 44°00' 0 25 Kilometers ^/T \~- ' < x Forest Other Base from U.S. Geological Survey digital data 1:100,000, 1990, Albers Equal-Area Conic Boundary of study area projection. Standard parallels: 29°30' and 45°30', central meridian: -93°00' Boundary of the Upper Mississippi River Basin study unit Well completed in the confined aquifer Well completed in the unconfined aquifer
Figure 5.--Land use and land cover in the Prairie du Chien-Jordan aquifer study area. Environmental-sample data were these analytes (major ions, nutrients, respective spike solutions. In addition to compared to quality-assurance data that DOC, trace metals, VOCs, and spike samples, surrogates comprised of were used to verify the effectiveness of pesticides). compounds similar in character to the cleaning methods of sampling equipment standard analytes were added to every and lack of cross contamination between Several major ions, nutrients, and pesticide and VOC sample before analy wells (blank samples). Replicate samples trace metals, including calcium, magne sis, to assess recoveries. were collected from selected wells to sium, sodium, silica, nitrate, ammonia, check the stability of water quality and to phosphorus, DOC, iron, zinc, manga Pesticides analyzed on Schedule 2010 check the efficacy of purging proce nese, barium, chromium, aluminum, generally had mean recoveries between dures. Spiked samples were submitted for nickel, and copper were detected at low 75 and 120 percent except for alachlor, selected pesticide and VOC samples to concentrations in some blank samples deethylatrazine, azinphos-methyl, benflu- measure changes in concentrations dur (table 3, in the Supplemental Information ralin, carbaryl, carbofuran, cyanazine, ing shipment and to check analytical section). Detected concentrations of ana p,p '-DDE, 2,6-diethylanaline, ethalflura- recoveries. lytes in the blank samples were far less lin, linuron, malathion, methyl parathion, than those reported in ground-water sam metolachlor, parathion, pendimenthalin, Twelve quality-assurance/quality- ples, indicating a low likelihood of cross- propanil, tebuthiuron, thiobencarb, and control (QA/QC) samples were col contamination of ground-water samples. trifluralin (table 4, in the Supplemental lected. These samples included three Low concentrations of trace metals in Information section). The mean recover field/equipment blanks, one VOC trip blanks may have been due to the stain ies for the 2010 surrogates (diazinon-dlO, blank, one source-solution blank, three less steel pump and stainless steel fittings a-HCH-£/6, and terbuthylazine) ranged spikes (pesticides and VOCs), and four in the sampling system, and the alumi from 103 to 133 percent (table 4, in the replicates. The standard NAWQA QA/ num foil used to wrap the pump between Supplemental Information section). Mean QC procedures are described in Koterba samples (Menheer and Brigham, 1997), recoveries in VOC spike samples ranged and others (1995). or to trace amounts of those metals in the from 69.3 to 115 percent (table 5, in the nitric acid preservative. When ground- Supplemental Information section). Mean Field/equipment blanks consisted of water samples were collected, larger vol VOC surrogate recoveries ranged from three types of water, prepared to be free umes of water were passed through the 77.7 to 111 percent for 1,2-dichloroet- of organic and inorganic compounds, sampling system prior to sample collec hane d-4; toluene d-8; and forp- which were pumped through the sam tion than when blanks were collected, bromofluorobenzene (table 5, in the Sup pling system. Field/equipment blanks which minimizes the concentrations of plemental Information section). Spike were used to determine whether cleaning metals contributed to samples by the and surrogate recoveries for both pesti procedures eliminated contamination sampling equipment. Thirteen VOCs cides and VOCs were generally within between sites and to ensure that field were detected in the field/equipment acceptable ranges. Concentrations of pes methods, sample shipment, and labora blanks, one VOC was detected in the trip ticides or VOCs in the environmental tory procedures had not contaminated blank, and 12 VOCs were detected in the samples were not adjusted for surrogate samples. Three field/equipment blanks source-solution blank (table 3, in the recoveries. (for major ions, nutrients, DOC, trace Supplemental Information section). All metals, pesticides, and VOCs) were taken but six of the concentrations of the A replicate sample is a sample col after a full cleaning and methanol/DI detected VOCs were reported as esti lected sequentially with a regular rinse of the equipment and sampling mated values, meaning that they were sample both are analyzed for the same lines. Trip blanks consisted of vials filled detected at concentrations below or near compounds (major ions, nutrients, DOC, with VOC-free blank water and sealed at reporting limits. Three VOCs chloro trace metals, radon, tritium, pesticides, the USGS National Water-Quality Labo form, methylene chloride, and and VOCs). The purpose of replicate ratory. Trip blanks were used to verify dichlorobromomethane were detect samples is to determine the sample vari that VOC vials were not contaminated able in the "VOC-free" blank water prior ability due to sample collection and during storage, sampling, or shipment to to its use. No pesticides were detected in laboratory analysis. Four replicate sam the laboratory. One VOC trip blank, con any of the blank samples. ples were analyzed for all parameters. sisting of three vials, was placed with Constituents with concentrations varying unused VOC vials in the field vehicle Spike samples were used to assess the by more than five percent between the used for sampling for six weeks and sub recovery bias and precision/variability in sample and replicate are listed in table 6, sequently shipped to the laboratory with recoveries of pesticides and VOCs. Extra in the Supplemental Information section. other samples. A source-solution blank water samples collected from three wells The differences in concentrations was prepared by filling sample bottles were spiked with known volumes of solu between the sample and replicate for directly with the blank water instead of tions containing known concentrations of these constituents were 0.2 mg/L or less running it through the sampling equip selected pesticides and VOCs. Two pesti for nutrients and dissolved organic car ment. Source-solution blanks are used to cide replicate samples and three VOC bon, 3.0 mg/L or less for major ions and check that the specially-prepared water replicate samples per well were spiked trace metals, 0.001 |ig/L or less for pesti was free of detectable concentrations of with the identical volumes of their cides, and 0.1 (ig/L or less for VOCs, and 50 picoCuries per Liter (pCi/L) or between 7.1 and 8.1 (table 1, in the Sup Calcium concentrations in water sam less for radon (table 6, in the Supplemen plemental Information section, fig. 6), ples were greater than those of the other tal Information section). due to buffering by carbonates in the major ions (table 7, in the Supplemental Summaries of water-quality data in aquifer. Specific conductances and alka- Information section, fig. 7). Calcium, this report include tables of median val linities were relatively high (mostly due which occurs only in the divalent (Ca+2) ues, standard deviations, ranges of to dissolution of dolomite), with medians oxidation state, occurs in ground water values, boxplots of selected-water qual of 560 and 482 microsiemens per centi primarily through dissolution of the rela ity constituents, statistical analyses of meter for specific conductances and 267 tively soluble carbonate minerals calcite differences in water quality between con and 216 mg/L as CaCO3 for alkalinities, and dolomite, and secondarily through fined and unconfined settings and in confined and unconfined portions of dissolution of the silicate minerals feld between the PDC and JDN portions of the PDCJ aquifer, respectively (table 1, in spar, pyroxene, and amphibole. the aquifer, and diagrams of major-ion the Supplemental Information section, Dissolution of dolomite ((Ca, Mg)CO3) composition. The nonparametric Mann- fig. 6). Specific conductances and alka in the PDC portion of the aquifer is the Whitney test (MW test) and the two sam linities were greater (the difference was most likely source of much of the cal ple t-test (t-test) were used to test for statistically significant at a 95 percent cium, magnesium, and alkalinity in water differences between groups. Censored confidence level (t-test)) in water in the samples from most of the wells. Rainfall values were set equal to zero. A confi confined portion of the aquifer. Dis is a minor source of calcium and other dence level of 95 percent was used to solved oxygen concentrations in water major ions including magnesium, indicate statistically significant from the wells ranged from less than 0.1 sodium, potassium, chloride, and sulfate differences. to 11.5 mg/L and tended to be greater in through entrainment of terrestrial dust in water samples from the unconfined por the atmosphere. Concentrations of these Acknowledgments tion of the PDCJ aquifer, although the ions in rainfall in the study area are typi differences were not statistically signifi The authors thank the private well cally less than 1.0 mg/L from samples in cant at a 95 percent confidence level (t- the upper Midwest in 1995 (National owners who volunteered their wells for test). Approximately half the dissolved sampling. Paul Hanson of the USGS pre Acidic Deposition Program/National oxygen concentrations were less than 1 Trends Network, electronic commun., pared maps and illustrations. Jack Bates mg/L (table 1, in the Supplemental Infor and Nadene Cable of the Wisconsin 1997). Calcium concentrations were mation section, fig. 6), indicating that slightly greater (but not at the 95 percent Department of Natural Resources assisted reduction processes such as denitrifica- in locating suitable wells for sampling in confidence level (t-test)) in water sam tion and sulfate reduction occur in ground ples from the confined portion of the Wisconsin. The authors also thank Rick water in the vicinity of some of the wells PDCJ aquifer, which may be a function Lindgren and David Saad of the USGS, in the unconfined portion of the aquifer. Roman Kanivetsky and Tony Runkel of of longer residence times and thus greater Water levels between confined and opportunity for dolomite dissolution. the Minnesota Geological Survey, Tom unconfined portions of the aquifer were Clark of the Minnesota Pollution Control statistically different at the 95 percent Magnesium concentrations were gen Agency, and Jim Walsh of the Minne confidence level (t-test); shallower water erally less, by a factor of two to three, sota Department of Health for reviewing levels were measured in wells completed than calcium concentrations (table 7, in this report. in the unconfined portion of the aquifer. the Supplemental Information section, fig. 7). Magnesium, like calcium, is a Ground-Water Quality Major Ions major ion which contributes to hardness of water. Hardness, an indicator of the Chemical analyses described in this Major ions analyzed in water sam ability of water to form insoluble resi report include physical parameters, major ples included calcium, magnesium, dues with soaps and to form scale in ions, nutrients, DOC, trace metals, radon, sodium, potassium, chloride, sulfate, flu- boilers and pipes, is calculated by multi tritium, pesticides, and VOCs. Results of oride, bromide, and silica (fig. 7). All plying the sum of milliequivalents per these analyses are described in this sec samples were calcium-magnesium-bicar liter of calcium and magnesium by 50, tion of the report. Data are available from bonate type waters (fig. 8). Major-ion and is expressed in mg/L of CaCO3 the USGS office in Mounds View, compositions of samples from this study (Hem, 1985). By the hardness scale of Minnesota. are similar to those of Nemetz (1993), Durfor and Becker (1964), most of the Physical Parameters and are similar to the calcium-magne water samples were "very hard" (greater sium-bicarbonate type water described by than 180 mg/L as CaCO3). The water in Physical parameters are summarized Wall and Regan (1994) and Smith and the confined portion of the PDCJ aquifer in table 1, in the Supplemental Informa Nemetz (1996) for the aquifer. Hardness, was significantly harder, at the 95 per tion section. Median depths to water were a water-quality variable important to cent confidence level (t-test), than water 83.5 and 28.0 ft below land surface in most water users, was calculated from the in the unconfined portion of the PDCJ confined and unconfined wells, respec concentrations of calcium and magne aquifer (table 7, in the Supplemental tively. The pH's were alkaline, ranging sium in the water samples. Information section). As with calcium,
10 DISSOLVED OXYGEN SPECIFIC CONDUCTANCE, ALKALINITY, IN MILLIGRAMS pH, IN STANDARD UNITS CONCENTRATION, IN IN MICROSIEMENS PER PER LITER AS CALCIUM MILLIGRAMS PER LITER CENTIMETER CARBONATE "-sj *«sj "*\| 00 oo GO -P" o> ""si 00 CO O o oo O) ro o (Q ooooo o o o o o o O) oo o o o o o C I i T CD O O
-oo.2. ro m 01 33^'<0 a
II o ol o ga? w m Q.-OO -t> o i i i i i i i i 0) =T = "35
TURBIDITY, IN DEPTH TO WATER, IN FEET NEPHELOMETRIC TEMPERATURE, IN BELOW LAND SURFACE TURBIDITY UNITS DEGREES CELSIUS CO Q) = 3 Q. (D .J » + ooooooooo o o o o o o *< 0.5 0.2 LU 0.1 zO o o 0.05 1 i Confined aquifer 0.02 Unconfined aquifer 0.01 i i o DISSOLVED MAJOR IONS EXPLANATION 25 Number of samples 90th percentile 75th percentile Median 25th percentile 10th percentile Reporting limit Figure 7.--Concentrations of dissolved major ions in water samples from Prairie du Chien-Jordan aquifer study area wells. 12 60 40 40 60 80 80 60 40 Calcium Chloride Calcium PERCENT MILLIEQUIVALENTS PER LITER PERCENT MILLIEQUIVALENTS PER LITER Confined Prairie du Chien-Jordan aquifer Unconfined Prairie du Chien-Jordan aquifer Figure 8.--Major ion composition of water samples from Prairie du Chien-Jordan aquifer study area wells. the primary source of magnesium in the dence level (t-test), in water from the nificant sources of sulfur include PDCJ aquifer is probably from the disso confined portion of the PDCJ aquifer, atmospheric emissions from volcanoes, lution of dolomite. Magnesium probably due to greater residence times combustion of fossil fuels, and smelting concentrations were greater, at the 95 and opportunity for dissolution of potas of ores (Hern, 1985). Greater sulfate con percent confidence level (t-test), in water sium-containing feldspars. centrations (but not at the 95 percent from the confined portion of the PDCJ confidence level (MW test)) and lesser aquifer (table 7, in the Supplemental Chloride concentrations ranged from dissolved oxygen concentrations in water Information section). 0.2 to 25 mg/L in water samples, with in the confined portion of the PDCJ aqui slightly greater concentrations in water fer indicate that oxidation of sulfide Sodium concentrations were gener from the unconfined portion of the PDCJ ally less than 10 mg/L (table 7, in the minerals may be a primary source of the aquifer (table 7, in the Supplemental sulfate in the PDCJ aquifer. Supplemental Information section, fig. Information section, fig. 7), but not at the 7). Significantly greater sodium concen 95 percent confidence level (MW-test). Concentrations of fluoride were less trations, at the 95 percent confidence Probable sources of anthropogenic chlo than 0.5 mg/L (table 7, in the Supplemen level (MW-test), in the confined portion ride in ground-water samples include tal Information section, fig. 7). Fluoride of the PDCJ aquifer may again be due to sodium chloride applied to de-ice high in ground water may be derived from dis longer residence times allowing longer ways in the winter and potassium solution of minerals such as fluorite, contact with and dissolution of sodium- chloride (KC1) fertilizers applied to crop fluoroapatite, amphiboles, micas, and containing minerals such as feldspars. land and lawns during the summer. feldspars in sedimentary rocks. Potassium concentrations were less Sulfate concentrations were greater Bromide concentrations were less than sodium concentrations by a factor of than chloride, sodium, and potassium than 0.2 mg/L (table 7, in the Supplemen about three (table 7, in the Supplemental concentrations, generally ranging from tal Information section, fig. 7). Bromide Information section, fig. 7). Potassium is 0.4 to 56 mg/L (table 7, in the Supple is similar in chemical behavior to chlo applied as a component of fertilizers and mental Information section, fig. 7). ride, but is much less abundant in natural is a common constituent in igneous and Sulfate (SO4~2) is the most common form waters (Hem, 1985). In addition to natu sedimentary rocks, primarily as grains or rally occurring bromide, bromide may of sulfur dissolved in oxygenated natural particles of feldspars and micas. Potas also be derived from ethylene dibromide, waters (Hem, 1985). In anoxic systems, sium is generally present in a widely-used gasoline additive and grain bacteria strip off oxygen from sulfate concentrations less than sodium in natu fumigant (Verschueren, 1983). ral waters because potassium is more anions, converting them to the relatively likely to be incorporated into clay min toxic hydrogen sulfide (^S) gas. Sulfur Silica concentrations ranged from 9.5 eral structures and is also an essential is widely distributed, in reduced form, as to 30 mg/L (table 7, in the Supplemental nutrient absorbed by plants (Hem, 1985). metallic sulfide minerals in igneous and Information section, fig. 7). Silicon is the Potassium concentrations were generally sedimentary rocks and as sulfate in the second-most abundant element in the greater, but not at the 95 percent confi mineral gypsum (Hem, 1985). Other sig earth's crust, exceeded only by oxygen 13 (Hem, 1985). Silicon forms strong bonds electronic commun., 1997). Nitrate con the Supplemental Information section, with oxygen, commonly forming SiO4 centrations exceeding 3 mg/L commonly fig. 9). indicate contamination by non-natural tetrahedra as building blocks of many Phosphorus concentrations in ground- sources (Madison and Brunett, 1984). igneous and metamorphic minerals. SiO2, water samples ranged from less than 0.01 Most nitrate concentrations in water sam the mineral quartz, is an important con to 0.07 mg/L (table 8, in the Supplemen ples collected for this study were less stituent in igneous rocks and sandstones. tal Information section, fig. 9). than 3 mg/L (table 8, in the Supplemen Silica concentrations were generally Phosphorus tends to be taken up by tal Information section, fig. 9), but the greater in wells completed in the con plants, and is also sorbed to organic mat MCL for nitrate (10 mg/L) was exceeded fined portion of the PDCJ aquifer (fig. 7), ter or to metallic oxides in soils and in the in two water samples from the uncon- but not at the 95 percent confidence level unsaturated and saturated zones. Because fined portion of the PDCJ aquifer and no (t-test), probably indicating that silica of sorption to organic and inorganic frac samples exceeded the MCL in the con progressively dissolves with greater resi tions in soils and sediments, phosphorus fined portion of the PDCJ aquifer. Nitrate dence times in the aquifer. concentrations in ground water are com was detected (at or above the reporting monly several orders of magnitude less limit) in 67 percent of water samples Nutrients and Dissolved Organic than nitrate concentrations. Sources of from wells in the confined portion of the Carbon phosphorus include minerals in igneous PDCJ and 84 percent of water samples and sedimentary rocks, animal wastes, from wells in the unconfined portion of The primary nutrients of concern in and detergents containing phosphorus the PDCJ. Nitrate concentrations were ground water are nitrate and phosphorus. generally greater in the unconfined por (Hem, 1985). Orthophosphate (PO4~3), Nitrate is typically reported as the sum of tion of the PDCJ aquifer than from wells the final dissociation product of phospho nitrite plus nitrate as nitrogen (NO2~ + in the confined portion (table 8, in the ric (H3PO4) acid, is one of many NO3~ as N). Because nitrite is usually Supplemental Information section, figs. chemical forms in which phosphorus detected in low concentrations, nitrite 9, 10); however, the difference was not occurs in natural waters. Orthophosphate plus nitrate will be referred to as "nitrate" statistically significant at the 95 percent is a form of phosphorus preferentially in this report. Elevated concentrations of confidence level (MW-test). Nitrate con taken up by plants and algae. Orthophos nitrate in drinking water (exceeding the centrations exceeded the USEPA MCL in phate concentrations generally were USEPA MCL of 10 mg/L as nitrogen) samples from two wells in agricultural equal to phosphorus concentrations, indi (U.S. Environmental Protection Agency, and urban areas where the aquifer is cating that Orthophosphate is the primary written commun., 1998) have been asso exposed at the land surface or where it form of phosphorus dissolved in water in ciated with "blue-baby" syndrome underlies thin deposits of outwash in the PDCJ aquifer. western Wisconsin and southeastern (methemoglobinemia), and with Dissolved organic carbon, resulting Minnesota. increased rates of stomach cancer, birth from DOC in rainfall and from the disso defects, miscarriage, and leukemia (For- lution of organic material in soils and man and others, 1985; Dorsch and others, Nitrate can be removed from water by the processes of denitrification and rock by percolating water and by ground 1984; Fan and others, 1987; National water, was detected in water samples Research Council, 1985). Nitrate and assimilation. Denitrification, which reduces nitrate to gases such as nitrous from all of the wells, generally in concen phosphorus discharged to surface water trations less than 1 mg/L (table 8, in the can also lead to eutrophication, which oxide (N2O) or dinitrogen (N2), is accomplished by bacteria or reduced Supplemental Information section, fig. depletes oxygen in lakes and rivers, lead 9). Although not a nutrient, DOC concen ing to increased mortality of oxygen- and forms of metals in oxygen-depleted water. Assimilation is the uptake of trations in water can affect dissolved temperature-sensitive native aquatic oxygen concentrations, causing changes species. nitrate and other nutrients by plant roots or by biota such as algae and bacteria, in redox conditions, which can affect Nitrate in ground water is principally and generally is limited to the soil zone. nutrient concentrations. derived from the following sources: natu Trace Metals ral mineral deposits (which do not occur Nitrite (NO2~) is an unstable interme in the study area), animal wastes, soils, diate product of nitrification which does Trace metals analyzed in water sam and fertilizers. Most nitrate results from not commonly occur in substantial con ples are listed in table 9, in the oxidation (nitrification) in soils of the centrations in ground water (Wall and Supplemental Information section. ammonia form of nitrogen (principally others, 1991) (table 8, in the Supplemen Although they are semi-metallic ele NH4+), which leaches from animal tal Information section, fig. 9). Because ments, arsenic, selenium, and antimony wastes, soils, and fertilizers. Nitrate con organic nitrogen and ammonia nitrogen are referred to as trace metals in this centrations in rainfall in the upper tend to sorb to organic matter or to clay report. Chemical conditions are often the Midwest ranged from 1.0 to 1.5 mg/L in particles, concentrations of these constit controlling factor in observed concentra 1995 (National Acidic Deposition Pro uents dissolved in the water were tions of these elements in ground water as gram/National Trends Network, relatively low or non-detected (table 8, in compared to the element's availability, as 14 IU . 1 1 1 1 1 1 1 I 1 1 1 25 ' t- 24 5 D Confined aquifer _ DC Unconfined aquifer EXPLANATION LU 24 = Number of MILLIGRAMSPERNLIT samples 24 25 pi So01ro_i 90th percentile 75th percentile O0 " Median 25th percentile Z 01 - O 2425 J r © 25 Hi 10th percentile o: 0.05 O Single sample l- : * 24 lB ~~ = value z 1 ^B ^H LJJ ~ 9 v p^-j ^H ' r ^B ~ Reporting limit g 0.02 HI ' O o 24 25 1 0.01 r-e--*- -e-^- - - 0.005 C (0 CO C ,'C C O C 0 3 3 0 .:± 0} Q) 'c O o ° | o rag5 o ag £ a. a ~ s^ * §^S C CO CO C OC C U 1 O O 4< ' "u 'c OL Q. c ro to > g 1 P 1 1 § 0 J E Q < E DISSOLVED NUTRIENTS Figure 9.--Concentrations of dissolved nutrients and dissolved organic carbon in water samples from Prairie du Chien-Jordan aquifer study area wells. suggested by the average abundance in or through the reduction of ferric hydrox samples exceeded the USEPA SMCL rocks (Hem, 1985). ides (Hem, 1985). Oxygen in ground 46 percent of water samples from the water can oxidize ferrous iron to the fer confined portion and 28 percent from the Iron was detected in the greatest con ric ion (Fe+~), which forms relatively unconfined portion. centrations of any of the trace metals insoluble ferric hydroxides (Hem, 1985). (table 9, in the Supplemental Informa Concentrations of zinc ranged from 3 tion section, fig. 11). Potential sources of Lesser dissolved oxygen concentrations to 659 H-g/L (table 9, in the Supplemental iron in ground water include minerals in the confined portion of the PDCJ aqui Information section, fig. 11). The concen common in bedrock or glacial deposits in fer inhibit formation of iron hydroxides, trations of zinc above background levels the study area pyroxenes, amphiboles, causing greater dissolved iron concentra (generally less than 10 |J.g/L) (Hem, biotite, magnetite, olivine, ferrous tions in those portions of the aquifer 1985) may be due to the use of galva polysulfides, siderite, and ferric oxides or (although not statistically significant at nized piping in the domestic well oxyhydroxide minerals (Hem, 1985). Iron the 95 percent confidence level (MW- systems. None of the zinc concentrations is also present in organic wastes and in test)) (table 9, in the Supplemental Infor exceeded the USEPA SMCL for zinc decaying plant debris and humic com mation section). Because iron hydroxide (5,000 n,g/L (table 9, in the Supplemen pounds in soils (Hem, 1985). Iron tends compounds stain laundry and plumbing tal Information section)). to be dissolved in ground water as the fixtures, the USEPA has established a Manganese concentrations ranged ferrous ion (Fe ), which is typically SMCL for iron of 0.3 mg/L (300 \ig/L) from less than 1 to 1,040 [ig/L (table 9, in released to ground water through the oxi (U.S. Environmental Protection Agency, the Supplemental Information section, dation of ferrous sulfides such as pyrite, 1996). Thirty-seven percent of all water fig. 11). Because of the tendency for 15 93°45' 93°30' 93°15' 93°00' 92°45' 92°30' 92° 15' 44°30' 45°15' 45°00' 44045. 44°30' Lake Pepin 44°15' Estimated extent of the confined Prairie du Chien-Jordan aquifer Estimated extent of the unconfined Prairie du Chien-Jordan aquifer 0 25 Miles 1 1 1 1 1 Boundary of the Prairie du Chien- 1 1 1 1 1 Jordan Aquifer study area 0 25 Kilometers 44°00' Boundary of the Upper Mississippi River Basin study unit Base from U.S. Geological Survey digital data 1:100,000, 1990, Albers Equal-Area Conic Nitrate nitrogen concentration in milligrams projection. Standard parallels: 29°30' and 45°30', per liter for wells completed in: central meridian: -93°00' Confined Unconfined aquifer aquifer Extent of the confined and unconfined Prairie du Chien- ...... A...... Greater than 10 Jordan aquifer used in this study was modified from Brown, 1988; Kanivetsky, 1978; Mudrey and others, ...... A...... 3 to 10 1987; Olcott,1992. O....~...... ~....~... A...... Less than 3 Figure 10.-Locations of wells and nitrate concentrations in water samples from wells completed in the Prairie du Chien-Jordan aquifer 16 - *«: . -<-« ,,.; «* . / i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i : IUUUU 5000 I 25 Samples for each IE Confined aquifer ~ ~ 2000 Unconfined aquifer ~ cc 1000 H ^~ _ -1 500 ~ oc t-- m - - u 200^ ^ 100 1- -_ : 0 50 cc o - ^ 20 - z ~ i © : Z. 10 O 0 J NCENTRAT fO(flj. 11 1 * ~- II +f hi 9 ~ - ^f 1 O 0 0 0 - 0 _ ~E o - 0.5 ~- -E 0.2 - - 0.1 II II 1 1 1 1 II 111 II 1 1 1 1 1 1 1 1 II II 1 2~0333-go.3D £.3Sj3o-S~.2 ~ § * | | * 8 | I S 1 ^ 5 I * ! 1 DISSOLVED TRACE METALS EXPLANATION 90th percentile 75th percentile Median 25th percentile 10th percentile o Single sample value Reporting limit Figure 11 .-Concentrations of trace metals in water samples from Prairie du Chien-Jordan aquifer study area wells. 17 black manganese oxide stains to form on mony, silver, cadmium, or beryllium water samples (64 percent of water sam laundry and plumbing fixtures, the (table 9, in the Supplemental Information ples from wells completed in the USEPA has set a SMCL of 50 |ig/L for section, fig. 11). Concentrations of these confined portion and 68 percent of water manganese (U.S. Environmental Protec trace metals were generally less than 5 samples from wells completed in the tion Agency, 1996). Water samples from |4,g/L. With the exception of lead, none of unconfined portion) had radon concentra 42 percent of the wells had manganese the detected concentrations of these trace tions that exceeded the withdrawn MCL. concentrations exceeding the USEPA metals exceeded MCLs or SMCLs estab Radon concentrations in water samples SMCL 52 percent of water samples lished by the USEPA (1996). Lead was from the confined and unconfined por from wells in the confined PDCJ and 32 detected in water samples from three tions of the PDCJ aquifer were not percent from wells in the unconfined wells in the confined PDCJ (all at con significantly different at the 95 percent PDCJ. Manganese redox-driven reac centrations of 2.0 |J,g/L). confidence level (t-test). tions are similar to those that occur with iron, but manganese is somewhat less Radon Tritium likely to precipitate in hydroxide com Radon gas ( 999 Rn) is a radioactive plexes (Hem, 1985). Manganese is a noble gas created by the decay of radium Tritium (3H), a radioactive hydrogen minor constituent in igneous rocks such isotopes 223, 224, and 226 (Hem, 1985). isotope, may replace normal hydrogen in as olivine, pyroxenes, and amphiboles The source of radon gas in ground water water molecules and breaks down to and small amounts of manganese (Hem, is the radioactive decay of naturally helium (He ) through emission of a P 1985) commonly substitute for calcium in (beta) particle and a neutrino. Tritium, limestones and dolomites. As with iron, occurring uranium in sediments and bed with a half-life of 12.43 years, is natu manganese concentrations tended to be rock. Radon is soluble in water and readily volatilizes. Radon has a half-life rally produced in the atmosphere by greater (but not at the 95 percent confi reactions between nitrogen and oxygen. dence level (MW test)) in the more of 3.8 days and decays to Pb by emit Anthropogenic sources of tritium include reducing, confined portion of the PDCJ ting three alpha particles through a series aquifer. of short-lived daughter isotopes (Hem, 1985). Ingestion of radon directly in 1100 Barium concentrations ranged from 1 drinking water probably does not pose a -0. 1000 25 to 329 (ig/L in water samples (table 9, in 25 serious health risk (Aieta and others, the Supplemental Information section, 900 1987; Cothern, 1987; Crawford-Brown, fig. 11). Barium is contained in the rela 800 1990). The primary risk posed by radon tively insoluble sulfate mineral barite is due to de-gassing into household air 700 (BaSO/j), and is also a common constitu LJJC/) (Wanty and Nordstrom, 1993). Radon OLU ent in metallic oxides and hydroxides can be absorbed by lung tissues and alpha Q - 500 (Hem, 1985). The USEPA drinking-water particles emitted during decay can cause Oo 400 MCL for barium of 2 mg/L (U.S. Envi damage to tissue. Prolonged respiration go 300 ronmental Protection Agency, 1996) was of high concentrations of radon gas have II not exceeded in any of the water samples. been linked to lung cancer (National 200 The trace metals chromium, alumi Research Council, 1988). Because of this 100 num, nickel, copper, and molybdenum risk, the USEPA proposed an MCL of 0 were detected in water samples from 300 pCi/L for drinking water. However, most of the wells, generally at concentra the MCL for radon was withdrawn in tions less than 10 ug/L (table 9, in the August 1996 as part of the reauthoriza- Supplemental Information section, fig. tion of the Clean Water Act, and is currently being reevaluated by the 11). Those metals may be partly attrib EXPLANATION uted to galvanized steel well casings and National Science Foundation (Safe water-supply pipes in the domestic well Drinking Water Hotline, oral commun., 25 Number of samples systems, stainless steel fittings in the 1997). 90th percentile 75th percentile water-sampling system, or the aluminum Radon concentrations in water sam foil used to wrap the pump after each ples ranged from about 100 to 1,000 pCi/ Median cleaning. None of the detected concentra L (figs. 12 and 13), similar to results of tions of these metals exceeded the other ground water studies (Wanty and 25th percentile respective USEPA MCLs (U.S. Environ Nordstrom, 1993). The median radon mental Protection Agency, 1996). concentration was 500 pCi/L from wells 10th percentile Water samples from less than one- completed in the confined portion of the Figure 12.--Concentrations of radon third of the wells had detectable concen PDCJ aquifer and 340 pCi/L from wells in water samples from Prairie trations of the trace metals uranium, completed in the unconfined portion of du Chien-Jordan aquifer study arsenic, selenium, lead, cobalt, anti the PDCJ aquifer. Sixty-six percent of area wells. 18 93°45' 93°00' 92°45' 92°30' 92°15' 44°30' 45°15' 45°00' 44045. 44030- Lake Pepin 44°15' Estimated extent of the confined Prairie du Chien-Jordan aquifer Estimated extent of the unconfined 0 25 Miles Prairie du Chien-Jordan aquifer 1 1 1 l 1 1 1 1 1 1 Boundary of study area Kilometers 44°00' 0 25 Boundary of the Upper Mississippi River Basin study unit Base from U.S. Geological Survey digital data 1:100,000, 1990, Albers Equal-Area Conic Radon concentration in picocuries per projection. Standard parallels: 29°30' and 45°30', liter for wells completed in the: central meridian: -93°00' Confined Unconfined aquifer aquifer Extent of the confined and unconfined Prairie du Chien- Jordan aquifer used in this study was modified from ...... A ...... Greater than 300 Brown, 1988; Kanivetsky, 1978; Mudrey and others, O~~....~...~....~~.~ A ...... Less than 300 1987; Olcott, 1992. Figure 13.--Locations of wells and radon concentrations in water samples from wells completed in the Prairie du Chien-Jordan aquifer. 19 nuclear reactors and detonations of fusion concentrations between confined and application and deposited at the land sur or thermonuclear weapons. Prior to the unconfined portions were not statistically face by atmospheric deposition over great advent of atmospheric testing of fusion significant at the 95 percent confidence distances (Spencer and Cliath, 1990; bombs in 1953, tritium concentrations in level (MW test). Both median concentra Majewski and Capel, 1995). Most pesti rainwater were approximately 2-8 tritium tions are in the range of mixed water, and cides are designed to stay in the soil zone. units (1 tritium unit (TU) = 1 tritium therefore probably include both pre-1953 Many are prone to sorb to solids and atom/10 hydrogen atoms) (Drever, and post-195 3 water recharge dates organic matter in soils, are degraded by 1988). During the 1960's, at the maxi (Alexander and Alexander, 1989). abiotic and biotic processes in the unsat- mum of atmospheric weapons testing, Pesticides urated zone, and have relatively low tritium concentrations in rainwater solubilities in water (Rao and Alley, increased to over 5,000 TU (Plummer Pesticides are compounds used to kill 1993). One or more pesticides were and others, 1993). Because of its short plant or insect pests. They are applied detected in 36 percent of water samples half-life and lack of atmospheric weap primarily to cropland in rural areas, but from wells in the confined PDCJ and 60 ons testing since the 1960's, tritium also for lawns, rights-of-way, and gar percent of water samples from wells in concentrations in rainfall are gradually dens in urban areas. A total of 47 the unconfined PDCJ (fig. 16). Differ decreasing to "pre-1953" levels. Because pesticide compounds (parent and break ences in the frequency of pesticide tritium produced by atmospheric testing down products), including several differ detections between the two groups were of fusion bombs is dissolved in ground ent classes of pesticides such as triazines, not statistically significant at the 95 per water, it is useful in determining relative organophosphorus, organochlorines, car- cent confidence level (MW test). Most of ground-water ages (Alexander and Alex bamates, and others, were analyzed in the wells with detections of pesticides ander, 1989). Current tritium water samples (table 10, in the Supple tend to be in the eastern portion of the concentrations in rainwater range from 5- mental Information section). Pesticides study area where the aquifer is closer to 20 TU (Jim Walsh, Minnesota Depart may also be volatilized during and after land surface and where glacial till confin ment of Health, oral commun., 1998). ing units are less extensive. 28 Tritium concentrations in ground water of 12 Atrazine and its metabolite (break less than 0.8 TU probably indicate that 13 1 24 down product) deethylatrazine were the the water was recharged prior to 1953; most commonly-detected pesticide com 0.8-10 TU probably indicate mixed prior- L_ £b 20 pounds in water samples (fig. 17). and post-195 3 water; greater than 10 TU Atrazine was detected in water samples probably indicate recharge after 1953 g, 16 from 36 percent of wells in the confined (Alexander and Alexander, 1989). As tri PDCJ and 52 percent of wells in the tium becomes less useful as an age-dating Ob 12 unconfined PDCJ, but the difference was Orr tool, it is being replaced by other age-dat not statistically significant at the 95 per ing constituents such as carbon-14 and cent confidence level (MW test). chlorofluorocarbons. r Detected concentrations of atrazine in the water samples were all less than 1 \ig/L Water samples from 25 wells were (table 11, in the Supplemental Informa analyzed for tritium concentrations to I tion section), except for one sample (2.8 evaluate whether water in the PDCJ aqui Hg/L), which was below the MCL of 3 fer has been recharged since 1953, and to u.g/L set by the USEPA for atrazine (U.S. evaluate whether water in the confined Environmental Protection Agency, 1996). portion of the aquifer is older than water No MCL has been established for deethy in the unconfined portion of the aquifer EXPLANATION latrazine (U.S. Environmental Protection (figs. 14 and 15). Tritium concentrations Agency, 1996). Atrazine is a triazine her in the water samples from the confined 13 Number of samples bicide used to control annual grasses in portion of the PDCJ aquifer ranged from i 90th percentile corn fields. less than 0.3 to 26.9 TU's (median=1.9), 75th percentile and tritium concentrations from the Median Additional pesticide compounds unconfined portion of the PDCJ aquifer detected in water samples included ranged from less than 0.3 to 29.4 TU's simazine, diazinon, metolachlor, alachlor, 25th percentile (median=6.9), probably indicating that and 2,6-diethylanaline (table 11, in the the water in the unconfined portion of the 10th percentile Supplemental Information section, fig. aquifer tends to be slightly younger than 17). All these compounds were detected water in the confined portion of the aqui Figure 14.-Concentrations of at concentrations less than 1 |J,g/L (except fer. Similar ranges in tritium tritium in water samples from diazinon in one sample, at 19 H-g/L) and concentrations were found by Wall and Prairie du Chien-Jordan none of their concentrations exceeded Regan (1994). The differences in tritium aquifer study area wells. established USEPA MCLs. Simazine is a 20 93=45' 93°30' 93°15' 93°00' 92°45' 92°30' 92°15' 44=30' - 45°15' - The Upper Mississipp River Basin study unit 45°00' - 44=45- _ 44030- 44°15' Estimated extent of the confined Prairie du Chien-Jordan aquifer Estimated extent of the unconfined Prairie du Chien-Jordan aquifer 0 25 Miles 1 1 1 l 1 Boundary of study area 1 1 1 1 1 44°00' 0 25 Kilometers Boundary of the Upper Mississippi 1 NT River Basin study unit Base from U.S. Geological Survey digital data Tritium concentration in tritium units for 1:100,000, 1990, Albers Equal-Area Conic wells completed in the: projection. Standard parallels: 29°30' and 45°30', central meridian: -93°00' Confined Unconfined aquifer aquifer Extent of the confined and unconfined Prairie du Chien- ...... A...... Greater than 10 Jordan aquifer used in this study was modified from ...... A...... 0.8 to 10 Brown, 1988; Kanivetsky, 1978; Mudrey and others, O-~~.-~...-~..~~-A...... Less than 0.8 1987; Olcott, 1992. Figure 15.-Locations of wells and tritium concentrations in water samples from wells completed in the Prairie du Chien-Jordan aquifer. 21 93°45' 93°30' 93°15' 93°00' 92°45' 92°30' 92°15' 44030- 45°15' The Upper Mississippi River Basin study unit 45°00' 44045- 44030- 44°15' Estimated extent of the confined Prairie du Chien-Jordan aquifer Estimated extent of the unconfined 0 25 Miles Prairie du Chien-Jordan aquifer 1 1 1 i 1 1 1 1 ' 1 Boundary of study area 44°00' 0 25 Kilometers Boundary of the Upper Mississippi River Basin study unit Base from U.S. Geological Survey digital data 1:100,000,1990, Albers Equal-Area Conic Pesticide compounds in wells projection. Standard parallels: 29°30' and 45°30', completed in the: central meridian: -93°00' Confined Unconfined aquifer aquifer Extent of the confined and unconfined Prairie du Chien- ...... A ...... Detection Jordan aquifer used in this study was modified from Brown, 1988; Kanivetsky, 1978; Mudrey and others, O.. .A. No detection 1987; Olcott, 1992. Figure 16.--Locations of Prairie du Chien-Jordan aquifer study area wells with water samples having detectable concentrations of pesticide compounds. 22 Wells completed in the Confined Prairie du Chien-Jordan aquifer Wells completed in the Unconfined Prairie du Chien-Jordan aquifer PESTICIDE COMPOUND Figure 17.-Frequencies of detection of pesticide compounds in water samples from Prairie du Chien-Jordan aquifer study area wells. triazine herbicide applied to corn crops vents, wood preservatives, dry-cleaning were not statistically significant at the 95 and in rights-of-way to control weeds. agents, pesticides, cosmetics, correction percent confidence level (MW test). Diazinon is a phosphorothioate com fluids, and refrigerants. VOCs may leach None of the concentrations of the 22 pound used as an insecticide and to ground water from spills and leaks at detected VOCs exceeded MCLs set by nematicide in both agricultural and urban or near the land surface, from atmo the USEPA for drinking water (U.S. areas. Metolachlor is a chloroacetanilide spheric dispersion into ground water, and Environmental Protection Agency, 1996). compound used as a preemergent herbi through recharge of rainwater which con The most frequently detected VOC in cide for corn, soybean, grain sorghum, tains VOCs sorbed from the atmosphere. sampled wells was carbon disulfide (table and potato crops (Sine, 1993). It is con Water samples from the wells were ana 13, in the Supplemental Information sec sidered to be a possible human lyzed for 87 VOCs from several chemical tion, fig. 19), with detections in water carcinogen, with a lifetime health advi groups (table 12, in the Supplemental samples from 26 wells. Carbon disulfide sory limit of 70 (J.g/L for drinking water Information section). VOCs were (U.S. Environmental Protection Agency, was detected more frequently in water detected in water samples from 41 of the samples from the confined portion of the 1996). Metolachlor is relatively soluble 50 wells, with almost all of those concen in water, is moderately volatile, has a rel PDCJ aquifer (60 percent) than in water trations being less than 0.5 jig/L (table samples from the unconfined portion of atively low sorption coefficient to organic 13, in the Supplemental Information sec carbon, and has a soil half-life of 40 days the PDCJ aquifer (44 percent) (table 13, tion, fig. 18). The concentrations tended in the Supplemental Information section, (Weber, 1994). Alachlor is a chloroaceta to be slightly greater in water samples nilide herbicide used as a preemergent fig. 19). All detected concentrations were from wells in the unconfined PDCJ. herbicide for corn and soybean crops and less than 0.1 |ig/L. No MCL for drinking These findings are consistent with results 2,6-Diethylanaline is a metabolite of water has been established for this com of analyses of existing data on VOC con alachlor. pound. Carbon disulfide is a colorless centrations that indicate a decrease in liquid with a slightly pungent, sulfurous Volatile Organic Compounds VOC concentrations with depths of sam odor which is used in the manufacture of pled wells (Andrews and others, 1995b). rayon, cellophane, carbon tetrachloride, VOCs are carbon-containing com Additionally, more types of VOCs were rubber, soil disinfectants, soil condition pounds that readily evaporate at normal detected in water samples from wells in ers, grain fumigants, herbicides, paper, temperature and pressure. VOCs are con the unconfined PDCJ (figs. 18 and 19). pharmaceuticals, electronic vacuum tained in many commercial products Differences in the frequency of VOC tubes, and as a solvent (Verschueren, including gasoline, paints, adhesives, sol detections between these two groups 1983). The relatively high frequency of 23 93°45' 93°30' 93°15' 93°00' 92°45' 92°30' 92°15' 44°30' 45°15' The Upper Mississippi River basin study unit 45°00' 44045' 44030- 44°15' Estimated extent of the confined Prairie du Chien-Jordan aquifer Estimated extent of the unconfined 0 25 Miles Prairie du Chien-Jordan aquifer 1 1 1 1 1 1 1 1 1 l Boundary of study area 25 Kilometers 44°00' 0 Boundary of the Upper Mississippi VTT River Basin study unit Base from U.S. Geological Survey digital data 1:100,000, 1990, Albers Equal-Area Conic Volatile organic compounds in wells projection. Standard parallels: 29°30' and 45°30', completed in the: central meridian: -93°00' Confined Unconfined aquifer aquifer Extent of the confined and unconfined Prairie du Chien- ...... A .... Detection Jordan aquifer used in this study was modified from Brown, 1988; Kanivetsky, 1978; Mudrey and others, O- . A...... No detection 1987; Olcott, 1992. Figure 18.--Locations of Prairie du Chien-Jordan aquifer study area wells with water samples having detectable concentrations of volatile organic compounds. 24 70 CU Wells completed in the Confined 60 Prairie du Chien-Jordan aquifer H Wells completed in the Unconfined b 50 Prairie du Chien-Jordan aquifer CO LLLU OU ofc£Q LU 20 O DC °-111 10 cu CD CD CD (D (D CD T3 T3 E E C T3 C C 0) CD CO CD N £ £ N O -C -C O O C *-'-*- W OJ .C CD CD o£ 1=o o o Sl-l-molifl E E & I _Q« I-!- I-*- 6 t^2 i IfS .2 O o o Q. O O -C O CM .2 Z D O VOLATILE ORGANIC COMPOUND Figure 19.-Frequencies of detection of volatile organic compounds in water samples from Prairie du Chien-Jordan aquifer study area wells. detection of this compound at low con and unconfined portions of the PDCJ methyl chloride as a possible human car centrations in ground water indicates a aquifer was similar (36 and 44 percent, cinogen and has established a lifetime widespread source. Carbon disulfide is respectively) (table 13, in the Supplemen health advisory of 3 jig/L in drinking naturally emitted from many soils, partic tal Information section, fig. 19). Methyl water (U.S. Environmental Protection ularly soils rich in organic matter and chloride is used in the manufacture of sil- Agency, 1996). None of the samples through bacterial interactions with sul- icone, tetraethyllead, synthetic rubber, exceeded that lifetime health advisory fide minerals such as pyrite methyl cellulose, refrigerants, methylene concentration. (Verschueren, 1983). Although emis chloride, chloroform, carbon tetrachlo- The compound 1,2,4-Trimethylben- sions from soils or by indigenous bacteria ride, and fumigants (Verschueren, 1983). zene was detected in water samples from may be important sources of carbon dis Methyl chloride is also used as a low 12 wells (table 13, in the Supplemental temperature solvent, in medicines, as ulfide, more information is needed to Information section, fig. 19). None of the fluid in thermostatic equipment, as an determine whether sources of this com detections exceeded 0.2 (J.g/L. This com extractant, as a propellant, and in herbi pound are natural or anthropogenic. pound is used in the manufacture of cides and medicines (Verschueren, 1983). trimellitic anhydride, dyes, pharmaceuti- Methyl chloride, also known as chlo- This VOC is also present in parts-per- cals, and pseudocumidine (Verschueren, romethane, was the second most thousand concentrations in cigarette 1983). It is also found in high octane gas frequently detected VOC (table 13, in the smoke (Verschueren, 1983). Low con oline (Verschueren, 1983). There are no Supplemental Information section, fig. centrations of methyl chloride may also MCLs or health advisories established for 19) with detections in water samples have been created by reactions between this compound. from 20 wells. None of the detected con naturally occurring organic matter in centrations exceeded 0.1 Ltg/L. The water samples and the drops of 1:1 Bromoform is a trihalomethane com frequency of detection of methyl chlo hydrochloric acid used to preserve the pound that was detected at low ride in water samples from both confined water samples. The USEPA has rated concentrations in water samples from 10 25 wells (table 13, in the Supplemental terf-butyl methyl ether (MTBE) (table 13, between confined and unconfined por Information section, fig. 19). None of the in the Supplemental Information sec tions of the aquifer, and leakage of water detections exceeded 0.2 [ig/L. Bromo- tion). All were detected in water samples from overlying units, is increased by allu form is used in the manufacture of from fewer than five wells, with concen vium and glacial outwash filled bedrock pharmaceuticals, fire-resistant chemicals, trations generally less than 0.5 |J.g/L. valleys eroded into the aquifer. In addi and as a solvent for waxes, greases, and None of the detected VOCs exceeded tion, the presence or absence of a 10- oils (Verschueren, 1983). Chlorination of MCLs. MTBE was detected in one water foot-thick (clay, glacial till or bedrock) water containing organic compounds sample (table 13, in the Supplemental confining unit, used as the criteria to forms trihalomethane compounds, includ Information section) at a concentration define confining units in this report, may ing bromoform. The USEPA has estimated to be 0.010 |Lig/L, which is not be sufficient to protect water in the established an MCL of 80 |ig/L for the below the reporting limit of 0.100 |0.g/L. aquifer from the influence of contami sum of the concentrations of the triha MTBE is used as a fuel oxygenate to nants resulting from land-use activities. lomethane compounds. reduce the atmospheric concentrations of To help ensure isolation from anthropo The trihalomethane compound chlo carbon monoxide or ozone. Possible genic contamination of wells completed roform was detected in water samples sources of MTBE include atmospheric in the aquifer, locating wells in areas with from seven of the wells (table 13, in the deposition, stormwater runoff, vehicles confining units greater than 10 feet in Supplemental Information section, fig. with gasoline purchased in areas that use thickness may be desirable. MTBE, or accidental contamination of 19). None of the detections exceeded 0.2 The textural composition of glacial- jig/L. Primary sources of chloroform the sample at the lab. MTBE is not known to be added to gasoline in the deposit confining units overlying the include pulp and paper mills, pharmaceu aquifer may play an important role in tical manufacturing plants, chemical study area, but is used and widely detected in ground water in the Denver, protection of water in the aquifer from manufacturing plants, sewage treatment contaminants resulting from land-use plants that emit chlorinated wastewater, Colorado, metropolitan area (Bruce and McMahon, 1996). activity. Glacial deposits in the western and water utility plants that chlorinate portion (associated with the Des Moines drinking water (Agency for Toxic Sub Implications of Water-Quality Lobe) are more clay-rich than glacial stances and Disease Registry, electronic deposits in the eastern portion of the commun., 1997). Minor sources of chlo Variability Between Confined study area (associated with the Superior roform include automobile exhaust, and Unconfined Portions of Lobe). These tills are frequently inter tobacco smoke, decomposition of trichlo- the Prairie du Chien-Jordan mixed and stratigraphic succession of the roethene, burning of plastics, and its use tills is complex. Therefore, the signifi as a pesticide (Agency for Toxic Sub Aquifer cance of the source of glacial tills in stances and Disease Registry, electronic isolating the PDCJ aquifer from anthro commun., 1997). Chloroform detected in Based on samples collected for this pogenic activity at the land surface could water samples from these wells may also study, water in the unconfined portion of not be evaluated. A thorough evaluation be residual from hypochlorite used to the PDCJ aquifer appear to be affected to of the distribution and extent of these gla sterilize new wells and to periodically a greater extent by anthropogenic activi cial till units would be important in reduce iron-bacteria buildup in well cas ties than water in the confined portion of understanding the susceptibility of the ings and plumbing systems. the aquifer. Water samples from wells aquifer to anthropogenic activity. Chlorobenzene was detected in water completed in the confined portion of the samples from five wells (table 13, in the aquifer tend to have slightly greater con Water-Quality Variability Supplemental Information section, fig. centrations of dissolution products of 19). This compound is used for solvent naturally occurring materials that occur in Between the Prairie du Chien recovery, dye manufacturing, and in the the aquifer and the water in that portion Group and the Jordan Sand manufacture of aniline, insecticides, phe of the aquifer generally has longer resi stone Portions of the Prairie nol, and chloronitrobenzene dence time. Some of the naturally (Verschueren, 1983). occurring and anthropogenic materials in du Chien-Jordan Aquifer the aquifer pose nuisances or potential Other VOCs detected include methyl- health hazards to consumers of water ene chloride (dichloromethane), Wells selected for sampling generally from the aquifer. trichlorofluoromethane (CFC-11), tetra- were constructed so that the open inter chloroethene (PCE), In general, differences in anthropo vals of the wells were isolated in either dichlorodifluoromethane (CFC-12), genic and naturally occurring materials in the PDC or JDN portions of the PDCJ methyl iodide, acetone, methyl ethyl water between confined and unconfined aquifer. Of the 50 wells sampled, 33 ketone, benzene, trichloroethene, chloro- portions of the PDCJ aquifer are small wells are completed in the PDC and 14 ethane, bromodichloromethane, and frequently the differences are not sta wells are completed in the JDN. Analy dibromochloromethane,/?-isopropyltolu- tistically significant at the 95 percent sis of water-quality data from these wells ene, 1,1,1-trichloroethane, toluene, and confidence level. Mixing of waters allows for a general comparison of waters 26 from the two stratigraphic units that com trations, but not to chloride and tritium level (MW test). Median concentrations prise the PDCJ aquifer. concentrations. of nitrate were greater in the PDC than in the JDN, but the differences also were Smith and Nemetz (1996), in a study The only significant differences, at the 95 percent confidence level (t-test and not statistically significant at the 95 per of water-quality along selected flow paths MW test), in physical parameters in water cent confidence level (MW test), in the PDCJ aquifer, did not find a major from wells completed in the PDC versus regardless of whether the units were con effect on major-ion chemistry between the JDN areas of the PDCJ aquifer sam fined or unconfined. There also were no the stratigraphic units comprising the pled for this study were that pH, calcium, statistically significant differences, at the aquifer. Results of their work, however, and magnesium were slightly greater in 95 percent confidence level (MW test), in indicated that ground water from the areas where the JDN was unconfined in pesticide detections between the PDC or PDC had greater concentrations of comparison to areas where the PDC was JDN. nitrate, chloride, and tritium, a predomi unconfined. There were no other statisti nance of areas with oxidizing conditions, cally significant differences, at the 95 Saturation indices can indicate which and shorter residence times. In compari percent confidence level (t-test and MW minerals may precipitate in aquifers. son, ground water from the JDN had test), in physical parameters among con Indices were calculated to determine ground water with lesser concentrations fined or unconfined portions of the PDC whether water in either the PDC or JDN of nitrate, chloride, and tritium, a pre with confined or unconfined portions of dominance of areas with reducing the JDN. There also were no statistically were saturated with mineral components conditions, and longer residence times. significant differences, at the 95 percent using the methods outlined by Parkhurst Statistical analysis indicated a significant confidence level (t-test), in the hardness (1995). Calcite was generally determined relation between the distribution of of water from wells completed in either to be oversaturated in both the PDC and nitrate, chloride, and tritium concentra the PDC or JDN, regardless of whether the JDN. The saturation indices in water tions, with well grouting, well depth, and the units were confined or unconfined. samples were found to be similar to those the presence of the overlying Decorah Median concentrations of chloride found by Smith and Nemetz (1996); there shale. The thickness and composition of were greater in the PDC than in the JDN, was little difference in mineral saturation the overlying glacial drift was shown to but the differences were not statistically among the PDC and JDN portions of the be significantly related to nitrate concen significant at the 95 percent confidence PDCJ aquifer. Summary and Conclusions major ions, nutrients, dissolved organic carbon, trace metals, radon, tritium, pesticides, and volatile organic compounds. The Prairie du Chien-Jordan (PDCJ) aquifer (Prairie du Differences in anthropogenic and naturally occurring materi Chien-Trempealeau aquifer in Wisconsin), composed of dolo als in water between confined and unconfined portions of the mite and sandstone of Cambrian to Ordovician age, is the PDCJ aquifer are small and frequently the differences are not principal bedrock aquifer in the Upper Mississippi River study significant at the 95 percent confidence level. Dissolved oxygen unit of the National Water-Quality Assessment (NAWQA) Pro concentrations were slightly less (not statistically significant at gram. The aquifer supplies approximately 75 percent of the the 95 percent confidence level (nonparametric Mann-Whitney ground water withdrawn in the area. As part of the NAWQA test)), and specific conductances and alkalinities were greater Program, 50 domestic wells completed in confined and uncon (statistically significant at the 95 percent confidence level (two fined portions of this aquifer were sampled for approximately sample t-test)), in water in the confined portion of the aquifer. 200 constituents during July, August, and September of 1996. In Concentrations of most major ions were generally greater in certain areas, the aquifer is overlain by bedrock or glacial depos water from the confined portion of the aquifer. its having low hydraulic conductivity (termed "confined portion" of the aquifer in this report). In other areas the aquifer is over Nitrate (nitrite plus nitrate as N) and phosphorus are the pri lain by glacial sand and gravel deposits having greater hydraulic mary nutrients of concern in ground water due to potential conductivity (termed "unconfined portion" of the aquifer in this effects on human health and streams and rivers. Nitrate may report). Differences in the hydrogeologic characteristics of these leach to ground water from fertilizers and animal wastes applied overlying units have potential to affect the downward move to the land surface. Nitrate concentrations were generally greater ment of water and of contaminants from the land surface into the in the unconfined portion of the PDCJ aquifer although the dif aquifer. The purpose of this report is to describe the chemical ferences were not statistically significant at the 95 percent characteristics of water in the PDCJ aquifer and to summarize confidence level (nonparametric Mann-Whitney test). In the the differences in water quality in confined and unconfined por unconfined portion of the PDCJ aquifer, nitrate in two samples tions of the aquifer. Twenty-five wells were sampled in each exceeded the maximum contaminant level of 10 milligrams per portion of the aquifer. Water samples from the wells were mea liter (mg/L). In the confined portion of the PDCJ aquifer no sam sured for physical parameters and analyzed for concentrations of ples exceeded the maximum contaminant level of 10 mg/L for 27 nitrate. Phosphorus concentrations were generally about an order samples from 36 percent of wells in the confined portion of the of magnitude less than nitrate concentrations. PDCJ aquifer and from 52 percent of wells in the unconfined Concentrations of iron and manganese in water samples from portion of the PDCJ aquifer, although the difference in detection the confined and the unconfmed portions of the PDCJ aquifer rates was not statistically significant at the 95 percent confi exceeded secondary MCLs established by the USEPA for drink dence level (nonparametric Mann-Whitriey test). Atrazine is an ing water in 37 and 42 percent of water samples, respectively. herbicide commonly applied to corn crops. Several of the other Frequencies of detection and detected concentrations of iron and detected pesticides, including simazine, metolachlor, and manganese were generally greater in the confined portion of the alachlor, are also applied to corn, which is commonly grown in aquifer, although the differences were not statistically signifi the study area. cant at the 95 percent confidence level (nonparametric Mann- Volatile organic compounds (VOCs) were detected in all but Whitney test and two sample t-test). Zinc concentrations were nine of the water samples, but none at concentrations exceeding relatively high in water samples from the PDCJ aquifer, possi 1 microgram per liter. Carbon disulfide, which may be naturally bly due to galvanized well casings and water-supply pipes in the emitted from soils and bacteria, and methyl chloride were the domestic wells sampled. most frequently-detected VOCs in water samples from the PDCJ Radon concentrations in water samples were greater than the aquifer. A greater number of VOCs were detected in water sam suspended MCL of 300 picoCuries per liter (pCi/L) in 66 per ples from the unconfined portion of the PDCJ aquifer and VOCs cent of the water samples. Radon concentrations were generally were detected at slightly greater concentrations in the uncon greater in water samples from the confined portion of the PDCJ fined portion of the aquifer, although the difference in detection aquifer, although the difference was not statistically significant rates was not statistically significant at the 95 percent confi at the 95 percent confidence level (two sample t-test). Median dence level (nonparametric Mann-Whitney test). radon concentrations were 500 and 340 pCi/L, confined and unconfmed, respectively. Water in the unconfined portion of the PDCJ aquifer in Min nesota and Wisconsin appears to be affected to a greater degree Tritium concentrations were analyzed in water samples from by anthropogenic activities than water in the confined portion of 25 of the 50 wells. Tritium concentrations in those samples indi the aquifer. Water samples from wells completed in the con cated that water in the unconfmed portion of the PDCJ aquifer fined portion of the aquifer tend to have slightly greater may have been recharged more recently than water in the con concentrations of dissolution products of naturally occurring fined portion of the PDCJ aquifer, although differences in materials in the aquifer and water in that portion of the aquifer tritium concentrations between confined and unconfined por generally has a longer residence time. Some of the naturally tions of the aquifer were not statistically significant at the 95 occurring and anthropogenic materials in the aquifer pose nui percent confidence level (nonparametric Mann-Whitney test). sances or potential health hazards to consumers of water from A total of seven different pesticide compounds were detected the aquifer. In general, however, differences in anthropogenic in water samples. Atrazine and its metabolite, deethylatrazine, and naturally occurring materials among confined and uncon were the most frequently detected pesticide compounds in water fined portions of the PDCJ aquifer are small and frequently not samples from the PDCJ aquifer. Atrazine was detected in water statistically significant. 28 References Brenton, R.W., and Arnett, T.L., 1993, Fan, A.M., Wilhite, C.C., and Book, Methods of analysis by the U.S. S.A., 1987, Evaluation of the nitrate Geological Survey National Water drinking water standard with Aieta, E.M., Singley, I.E., Trussel, A.R., Quality Laboratory Determination reference to infant Thorbjarnarson, K. W., and McGuire, of dissolved organic carbon by UV- methemoglobinemia and potential M.J., 1987, Radionuclides in promoted persulfate oxidation and reproductive toxicity: Regulatory drinking water An overview: infrared spectrometry: U.S. Toxicology and Pharmacology, v. 7, Journal of the American Water Geological Survey Open-File Report p. 135-137. Works Association, v. 79, 92-480, 12 p. p. 144-152. 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Minnesota, North Dakota, and South and Applications, High Tatras, Dakota, 1993-95: U.S. Geological Czechoslovakia, October 1975 Sine, C., ed., 1993, Farm chemical Survey Water-Resources [Proceedings], 6 p. handbook '93: Meister Publishing Investigations Report 96-4317, 34 p. Parkhurst, D.L., 1995, User's guide to Company, Willoughby, Ohio, Metropolitan Council, 1992, Twin Cities PHREEQC--C computer program for variously paged. speciation, reaction-path, advective- Metropolitan Area water supply A Smith, S.E., and Nemetz, D.A., 1996, plan for action: Metropolitan transport, and inverse geochemical Water quality along selected flow Council, no. 590-92-025, St. Paul, calculations: U.S. Geological Survey paths in the Prairie du Chien-Jordan Minnesota, 72 p. Water-Resources Investigations Report 95-4227, 143 p. aquifer, southeastern Minnesota: Meyer, G.N, and Hobbs, H.C., 1989, Plummer, L.N., Michel, R.L., Thurman, U.S. Geological Survey Water- Surficial Geology, in Balaban, N.H., Resources Investigations Report 95- ed., Geologic Atlas Hennepin E.M., and Glynn, P.O., 1993, 4115, 76 p. County, Minnesota: Minnesota Environmental tracers for age-dating young ground water, in Alley, W.M., Geological Survey County Atlas Spencer, W.F., and Cliath, M.M., 1990, Series, C-4, 8 pis. Regional ground-water quality: Van Nostrand Reinhold, New York, p. 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W.M., ed., Regional ground-water S.G., and Fehlberg, K.M., 1995, Verschueren, Karel, 1983, Handbook of quality: Van Nostrand Reinhold, New York, p. 423-441. Methods of analysis by the U.S. environmental data on organic Geological Survey National Water chemicals: New York, Van Nostrand Weber, J.B., 1994, Properties and Quality Laboratory Determination Reinhold, 1310 p. behavior of pesticides in soil, in of pesticides in water by C-18 solid Wall, D.B., Montgomery, B.R., Deluca, Honeycurt, R.C, and Schabacker, phase extraction and capillary D., Meyers, G., and Thomas, D., D.J., eds., Mechanisms of pesticide column gas chromatography/mass 1991, Nitrogen in Minnesota ground movement into ground water: Lewis spectrometry with selected-ion water. Prepared for the Legislative Publishers, Boca Raton, Fla., monitoring: U.S. Geological Survey Water Commission: Minnesota p. 15-41. Open-File Report 95-181, 60 p. 31 32 Supplemental Information 33 Table 1. Medians, standard deviations, and ranges in well characteristics and values of physical parameters in water samples from Prairie du Chien-Jordan study area wells [uS/cm, microsiemens per centimeter; mg/L, milligrams per liter; <, less than; NTU, nephelometric turbidity units] Well Unconfined portion of aquifer Confined portion of aquifer characteristic or Units physical Standard Standard Median Range Median Range parameter deviation deviation Well depth Feet below land 180 92 66-340 200 94 105-400 surface Casing depth Feet below land 126 86 40-301 175 92 68-360 surface Depth to water1 Feet below land 28.0 54.3 13.4-218.1 83.5 56.2 13.4-214 surface Water temperature °Celsius 12.4 1.9 9.8-16.7 12.7 2.7 9.5-18.8 pH pH units 7.5 0.2 7.1-8.1 7.4 0.2 7.1-7.9 Specific conduc u,S/cm at 25 °C 482 120 310-742 560 154 287-856 tance Dissolved oxygen mg/L 1.7 3.4 O.1-10.5 0.5 3.8 <0.1-11.5 concentration Turbidity NTU 1.5 8.9 0.15-44 1.9 2.4 0-12.4 Alkalinity mg/L as 216 62 117-373 267 94 113-438 CaCO3 'Water levels measured in 14 of 25 wells completed in unconfined portions of the aquifer and in 15 of 25 wells completed in confined por tions of the aquifer. Table 2. Laboratory analysis methods for measured water-quality constituents Constituent or constituent Analysis method Reference group Major ions Atomic absorption spectrometric Fishman(1993) (USGS schedule 2750) Nutrients Various methods Fishman(1993) (USGS schedule 2752) Dissolved organic carbon UV-promoted persulfate oxidation and infra- Brenton and Arnett (1993) (USGS schedule 2085) red spectrometry Atomic absorption spectrometric Fishman(1993) Radon Liquid scintillation American Society for Testing (USGS labcode 1369) and Materials (1996) Tritium Electrolytic enrichment with gas counting Ostlund and Dorsey (1975) (USGS labcode 1565) Pesticides Solid-phase extraction using a C-18 cartridge Zaugg and others (1995) (USGS schedule 2010) and gas chromatography/mass spectrometry Volatile organic compounds Purge and trap capillary-column gas chroma Rose and Schroeder (1995) (USGS custom method 9090) tography/mass spectrometry 34 Table 3. Reporting limits and concentrations of analytes in blanks [na, not analyzed; E, detection with estimated concentration; --, not detected] Concentration Volatile organic Field/equipment Source solution Compound Reporting limit and unit compounds trip blanks blank blank Calcium 0.02 mg/L 0.03-0.16 na -- Magnesium .Olmg/L 0.02-0.03 na - Sodium .20 mg/L 0.20 na -- Silica .01 mg/L 0.07-0.32 na 0.06 Nitrate-nitrogen .050 mg/L 0.090 na 0.070 Ammonia-nitrogen .015 mg/L - na 0.020 Phosphorus .010 mg/L 0.050 na - Dissolved organic carbon .1 mg/L 0.40-13 na - Iron 3.0 ug/L 3.0 na - Zinc 1.0 ug/L 5.0-36 na - Manganese l.Ojig/L 1.0-2.0 na - Barium l.Ofig/L 31.0-5.0 na - Chromium 1.0 ug/L 2.0 na ~ Aluminum 1.0 ug/L 3.0-9.0 na 3.0 Nickel 1.0 ug/L 1.0 na - Copper 1.0 ug/L 2.0-3.0 na - Carbon disulfide .050 ug/L E0.010-E0.040 ~ E0.040 Methyl chloride .200 ug/L - E0.010 - 1 ,2,4-Trimethylbenzene .200 ug/L E0.020 ~ E0.010 Chloroform 1 .050 ug/L E0.060-E0.070 ~ 0.260 Chlorobenzene .050 ug/L E0.002 - E0.090 Methylene chloride 1 .100|ig/L E0.060 - E0.130 Tetrachloroethene .050 ug/L E0.002 - E0.010 Methyl ethyl ketone 5.00 ug/L 1.20-3.80 - E1.30 Acetone 5.00 ug/L El. 90-4.20 - - Benzene .050 |ig/L E0.050 ~ - Toluene .050 ug/L EO.050-0.250 - 0.120 1 ,2-Dichlorobenzene .050 U£/L -- - E0.020 1 ,3-Dichlorobenzene .050 ug/L - - E0.007 1 ,4-Dichlorobenzene .050 ug/L - - E0.020 Styrene .050 ug/L E0.010 - E0.030 orr/zo-Xylene .050 ug/L E0.009 - - Methyl isobutyl ketone 5.00 [ig/L E0.200-E0.300 - ~ These compounds were also detected by the lab in certification tests of the blank water used. 35 Table 4. Reporting limits and percent recoveries for schedule 2010 pesticide spikes l, micrograms per liter; nd, not determined] Mean percent recovery Range in Reporting Compound percent Spike #1 Spike #2 Spike #3 limit (|ig/L) recovery Acetochlor 0.002 102-115 114 113 102 Alachlor .002 113-128 126 124 115 Atrazine .001 90.3-112 109 107 93.0 Azinphos-methyl .001 117-198 159 192 122 Benfluralin .002 119-138 127 130 125 Butylate .002 78.8-109 99.2 90.1 80.9 Carbaryl .003 182-213 203 212 193 Carbofuran .003 150-186 167 182 154 Chlorpyrifos .004 94.3-103 97.3 99.9 95.8 Cyanazine .004 131-139 134 134 137 Dacthal (DCPA) .002 103-124 106 103 120 p,p '-DDE .006 66.7-79.1 69.0 67.8 75.0 Deethylatrazine .002 48.3-95.3 55.3 71.8 80.2 Diazinon .002 103-111 109 108 104 Dieldrin .001 80.1-95.2 94.8 94.2 80.2 2,6-Diethylanaline .003 69.3-83.7 70.9 81.6 70.7 Disulfoton .017 11.5-86.4 82.8 19.1 81.7 EPIC (eptam) .002 78.2-97.4 90.4 90.6 78.4 Ethalfluralin .004 128-151 142 143 133 Ethoprop .003 108-126 112 109 121 Fonofos .003 103-107 103 106 105 a-HCH .002 93.1-111 94.0 98.5 109 y-HCH (lindane) .004 93.1-110 94.4 101 108 Linuron .002 142-172 157 168 150 Malathion .005 131-143 134 141 138 Methyl parathion .006 139-167 162 162 150 Metolachlor .002 126-136 133 128 129 Metribuzin .004 107-127 114 118 112 Molinate .004 81.5-113 99.7 93.9 87.1 Napropamide .003 101-105 104 103 103 Parathion .004 124-143 131 135 133 36 Table 4. Reporting limits and percent recoveries for schedule 2010 pesticide spikes-Continued [pg/L, micrograms per liter; nd, not determined] Pebulate .004 75.4-105 97.5 90.8 79.1 Pendimethalin .004 112-135 126 127 117 cw-Permethrin .005 80.8-106 100 97.9 84.8 Phorate .002 82.7-104 94.4 85.7 104 Prometon .018 90.0-114 113 108 92.7 Pronamide .003 109-123 109 115 119 Propachlor .007 106-155 131 113 116 Propanil .004 122-138 126 123 134 Propargite .013 89.6-105 102 96.7 93.0 Simazine .005 97.6-113 111 108 102 Tebuthiuron .010 137-179 163 154 147 Terbacil .007 84.4-131 117 114 92.2 Terbufos .013 93.2-107 101 93.3 106 Thiobencarb .002 115-123 122 121 116 Triallate .001 88.3-106 102 103 89.0 Trifluralin .002 118-144 132 136 125 Surrogates a-HCH-^6 nd 102-130 103 107 127 Diazinon-JlO nd 113-127 125 120 117 Terbuthylazine nd 121-141 131 123 133 37 Table 5. Reporting limits and percent recoveries for custom method 9090 volatile organic compound spikes [pg/L, micrograms per liter; nd, not determined] Mean percent recovery Range in , Reporting Compound ,. ... ° percent Spike #1 Spike #2 Spike #3 F limit (u.g/L) recovery Bromodichloromethane 0.100 78.3-104 91.3 94.7 104 Bromoform .200 84.2-110 91.2 103 108 Carbon tetrachloride .050 66.7-117 83.3 87.5 114 Dibromochloromethane .100 78.3-104 86.9 94.5 100 1 ,4-Dichlorobenzene .050 64.0-84.0 76.0 69.3 82.7 1 ,2-Dichloroethane .050 92.0-116 98.7 96.0 115 1 , 1 -Dichloroethene .100 75.0-121 84.7 90.3 115 Ethylbenzene .050 65.4-96.1 83.3 79.5 83.3 MTBE .100 86.9-104 88.4 101 104 Tetrachloroethene .050 70.0-100 88.3 95.0 88.3 1,1,1 -Trichloroethane .050 70.8-95.8 84.7 84.7 94.4 Trichloroethene .050 69.6-95.7 86.9 88.4 92.7 Vinyl chloride .100 66.7-104 80.2 74.1 91.3 Surrogates /j-Bromofluorobenzene nd 77.0-95.0 84.3 77.7 94.7 1 ,2-Dichloroethane d-4 nd 94.0-112 97.0 97.3 111 Toluene J-8 nd 95.0-101 99.3 95.0 96.3 38 Table 6. Reporting limits and concentrations of compounds with greater than five percent differences in concentrations in replicate samples [mg/L, milligrams per liter; pg/L, micrograms per liter; E, detection with estimated concentration; --, less than five percent difference; <, less than; pCi/L, picoCuries per liter] Sample/replicate concentrations Reporting Compound ,. .f , . Replicate #1 Replicate #2 Replicate #3 Replicate #4 limit and unit ^ Nitrite-nitrogen 0.0 10 mg/L O.010/ 0.010 - Phosphorus .010 mg/L 0.010 / 0.020 0.010 /O.010 Dissolved organic carbon .10 mg/L 0.40 / 0.60 0.40 / 0.50 0.40 / 0.30 Calcium .02 mg/L 40 / 37 - -- Sodium .20 mg/L 2.2/2.4 -- Potassium .10 mg/L 0.80/0.90 1.3/1.2 - Chloride .10 mg/L 4.0/3.8 0.50/0.60 ~ Bromide .01 mg/L 0.090 / 0.070 -- Iron 3.0 ug/L 9.0/11 ~ Barium 1.0 Ug/L 4.0/3.0 - Chromium l.Oug/L 7.0/6.0 3.0/2.0 -- Copper 1.0 ug/L 19/17 1.0/<1.0 - Molybdenum l.Oug/L 1.0/2.0 - Nickel l.Oug/L 1.0/<1.0 2.0/3.0 ~ Zinc 1.0 ug/L 3.0/4.0 40/38 ~ Aluminum l.Oug/L 4.0/3.0 5.0/3.0 - Radon 80.0 pCi/L 690 / 740 230 / 280 190/170 Atrazine .001 ug/L 0.009/0.010 ~ Deethylatrazine .002 ug/L E0.004 / E0.005 ~ Chlorobenzene .050 ug/L - E0.001/<0.050 Methyl chloride .200 ug/L O.200/E0.010 E0.010/ 0.200 Tetrachloroethene .050 ug/L E0.004 / E0.005 -- Carbon disulfide .050 ug/L E0.080 / E0.050 E0.008 / E0.007 Methyl ethyl ketone 5.0 ug/L E0.200/E0.100 - 39 Table 7. Medians, standard deviations, and ranges in values of concentrations of major ions dissolved in water samples from Prairie du Chien-Jordan study area wells [Concentrations in mg/L] Unconfined portion of aquifer Confined portion of aquifer Constituent Standard Standard Median Range Median Range deviation deviation Calcium 62 ' 16.9 36-93 69.5 19.3 32-98 Magnesium 24 6.2 14-35 29 9.3 14-47 Hardness, as CaCC^ 253 65 153-376 282 82 137-438 Sodium 3.4 1.8 1.9-11 5.1 7.2 1.9-30 Potassium 1.2 0.6 0.6-3 1.4 1.0 0.5-3.6 Chloride 3.7 6.3 0.2-20 1.5 6.3 0.2-25 Sulfate 16 12.7 0.4-56 21 13.6 0.8-53 Fluoride 0.1 0.1 <0. 10-0.4 0.2 0.1 <0. 10-0.3 Bromide 0.04 0.02 0.02-0.09 0.04 0.02 0.02-0.11 Silica 18 4.5 11-26 19.5 5.3 9.5-30 Table 8. Number of samples with detectable concentrations, reporting limits, median values, standard deviations, and ranges in concentrations of nutrients and dissolved organic carbon in water samples from wells in the unconfined and confined portions of the Prairie du Chien-Jordan study area [Concentrations in mg/L; values for confined portion of the aquifer in parentheses] Number of samples with Reporting Standard Constituent Median Range detectable limit deviation concentrations1 Nitrite-nitrogen 11(2) 0.010 <0.01 (<0.01) 0.005 (0.003) <0.01-0.01 (<0.0 1-0.01) Ammonia-nitrogen 22 (22) .015 0.02 (0.09) 0.19(0.26) <0.015-0.94 (<0.015-0.77) Ammonia + organic-nitrogen 2(10) .20 <0.20 (<0.20) 0.2 (0.3) <0.20-1.0 (<0.20-0.80) Nitrate-nitrogen 21 (16) .050 0.64 (0.09) 4.23 (2.28) <0.05-17.0 (<0.05-8.4) Phosphorus 10(11) .01 <0.01 (<0.01) 0.02 (0.02) <0.01-0.07 (<0.01-0.07) Orthophosphorus 22 (17) .01 0.02 (0.02) 0.02 (0.01) <0.01-0.07 (<0.0 1-0.04) Dissolved organic carbon 25 (25) .10 0.5 (0.7) 0.3 (0.4) 0.20-1.5 (0.30-1.8) 'Samples from 25 wells completed in the unconfined portion of the Prairie du Chien-Jordan aquifer were analyzed for nutrients. Samples from 24 of 25 wells completed in the confined portion of the Prairie du Chien-Jordan aquifer were analyzed for nutrients; all samples were analyzed for dissolved organic carbon. 40 Table 9. Number of samples with detectable concentrations, reporting limits, median values, standard deviations, ranges in concentrations, and maximum contaminant levels of trace metals in water samples from wells in the unconfined and confined portions of the Prairie du Chien-Jordan study area [Concentrations in micrograms per liter (ug/L); values from the confined portion of the aquifer in parenthesis;--, not applicable; <, less than; MCL, Maximum Contaminant Level; SMCL, Secondary Maximum Contaminant Level] Number of samples with Reporting ., ,. Standard MCL or Trace metal Median , . . Range detectable limit deviation SMCL concentrations Iron 17(19) 3.0 12(180) 835(1,212) <3.0-3500 '300 (<3. 0-4,300) Zinc 25 (25) 1.0 85(13) 77(155) 12-290 '5,000 (3.0-659) Manganese 17(19) 1.0 4.0(61) 170(220) <1. 0-770 '50 (<1. 0-1, 040) Barium 24 (25) 1.0 28 (27) 73 (71) 1.0-329 2,000 (1.0-237) Chromium 24 (25) 1.0 4.0(5.0) 1.5(1.7) <1. 0-7.0 100 (2.0-7.0) Aluminum 24 (25) 1.0 3.0 (3.0) 2.6 (0.4) None (2.0-4.0) Copper 14(11) 1.0 3.0(<1.0) 10.5(8.0) <1.0-35 '1,000 (< 1.0-23) Nickel 24(23) 1.0 2.0(2.0) 4.0(1.1) <1.0-22 None (<1. 0-4.0) Molybdenum 10(15) 1.0 <1.0(1.0) 1.7(1.3) <1.0-8.0 None (< 1.0-4.0) Uranium 7(9) 1.0 <1.0(<1.0) 1.1(1.3) <1.0-5.0 220 (<1. 0-4.0) Arsenic 3(3) 1.0 <1.0(<1.0) 0.6(1.5) <1.0-3.0 50 (<1. 0-7.0) Selenium 2(2) 1.0 <1.0(<1.0) 0.3(0.5) 50 (<1. 0-2.0) Lead 0(3) 1.0 <1.0(<1.0) --(0.7) Nondetectable (<1. 0-2.0) Cobalt 2(0) 1.0 <1.0(<1.0) 0.8 (--) <1. 0-4.0 None (<1.0) Antimony 0(0) 1.0 <,.(,«!,) -(-) 6 (<1.0) Beryllium 0(0) 1.0 <1.0(<1.0) --(--) 4 (<1.0) Cadmium 0(0) 1.0 <1.0(<1.0) --(--) 5 (<1.0) Silver 0(0) 1.0 <1.0(<1.0) --(--) '100 (<1.0) 'SMCL 41 Table 10. Pesticide compounds analyzed in water samples, by chemical class Triazines Phosphorothioates Carbamates Atrazine Diazinon Butylate Cyanazine Chloroacetanilides Carbaryl Deethylatrazine Alachlor Carbofuran Metribuzin 2,6-Diethylanaline EPTC (Eptam) Prometon Metolachlor Molinate Simazine Sulfite Ester Pebulate Pyrethroid Propargite Thiobencarb cw-Permethrin Organochlorines Triallate Phenyl Ureas p-p'-DDE Dinitroaniline Linuron Dieldrin Benfluralin Tebuthiuron a-HCH Ethalfluralin Organophosphorus Y-HCH (Lindane) Pendimethalin Azinphos-methyl Amides Trifluralin Disulfoton Napropamide Hydroxy Acid Ethoprop Pronamide Terbacil Fonofos Propachlor Pyridazinone Malathion Propanil Chlorpyrifos Methyl parathion Acetanilides Other Parathion Acetochlor Dacthal (DCPA) Phorate Terbufos 42 Table 11. Reporting limits, number of samples with detectable concentrations, ranges in concentrations, and maximum contaminant levels of pesticide compounds in water samples from Prairie du Chien-Jordan study area wells [pg/L, micrograms per liter; E, detection with estimated concentration] Unconfined portion of aquifer Confined portion of aquifer Number (and Number (and Maximum Reporting percent) of Range in percent) of water Range in contaminant Compound limit samples with concentration samples with concentration level (|ig/L) detectable (jig/L) detectable (Hg/L) concentrations concentrations Atrazine 0.001 13 (52%) 0.001-2.80 9 (36%) O.001-0.344 3.0 Deethylatrazine .002 14 (56%) O.002-E0.616 9 (36%) O.002-E0.325 None Simazine .005 3 (12%) O.005-0.010 2 (8%) O.005-0.036 4.0 Diazinon .002 2 (8%) O.002-0.026 2 (8%) 0.002-19.0 None Metolachlor .002 1 (4%) O.002-0.004 1 (4%) O.002-0.012 None Alachlor .002 1 (4%) O.002-1.30 0 O.002 2.0 2,6-Diethylanaline .003 1 (4%) O.003-E0.003 0 O.003 None 43 Table 12. Volatile organic compounds analyzed in water samples, by chemical class Halogenated Alkanes Halogenated Alkenes Alkylated Benzenes Bromomethane 3 -Chloropropene /z-Butylbenzene Chloroethane 1,1 -Dichloroethene sec-Butylbenzene 1,2-Dibromo-3-chloropropane cis- 1,2-Dichloroethene ferf-Butylbenzene 1,2-Dibromoethane trans- 1,2-Dichlorethene 2-Chlorotoluene 1,1 -Dichloroethane 1,1 -Dichloropropene 4-Chlorotoluene 1,2-Dichloroethane cis-l ,3-Dichloropropene Ethylbenzene 1.2-Dichloropropane trans- 1,3-Dichloropropene o-Ethyl toluene 1.3-Dichloropropane Hexachlorobutadiene Isopropylbenzene 2,2-Dichloropropane Tetrachloroethene p-Isopropyltoluene Hexachloroethane Trichloroethene n-Propylbenzene Methyl chloride (Chloromethane) Vinyl bromide (Bromoethene) 1.2.3.4-Tetramethylbenzene Methylene chloride (Dichloromethane) Vinyl chloride (Chloroethene) 1.2.3.5-Tetramethylbenzene 1,1,1,2-Tetrachloroethane Alkenes Toluene 1,1,2,2-Tetrachloroethane Vinyl acetate 1.2.3-Trimethylbenzene 1,1,1 -Trichloroethane Halogenated Anomalies 1.2.4-Trimethylbenzene 1,1,2-Trichloroethane Bromobenzene 1,3,5-Trimethylbenzene 1,2,3-Trichloropropane Chlorobenzene meta- and para-Xylene Chlorofluorocarbons 1.2-Dichlorobenzene orr/zo-Xylene Dichlorodifluoromethane (CFC-12) 1.3-Dichlorobenzene Ethers Tetrachloromethane (Carbon tetrachloride) 1.4-Dichlorobenzene ten-Butyl ethyl ether Trichlorofluoromethane (CFC-11) Methyl iodide tert-Butyl methyl ether (MTBE) 1,1,2-Trichlorotrifluoromethane (CFC-113) 1.2.3-Trichlorobenzene Diethyl ether Aldehydes 1.2.4-Trichlorobenzene terf-Pentyl methyl ether Acrolein Aromatic Hydrocarbons Tetrahydrofuran Acrylonitrile (2-Propenitrile) Benzene Others Ketones Naphthalene Acetone 2-Butanone (Methyl ethyl ketone) Styrene Carbon disulfide 2-Hexanone Trihalomethanes trans-l ,4-Dichloro-2-butene Methyl isobutyl ketone (Hexanone) Bromochloromethane Diisopropyl ether Bromodichloromethane Ethyl methacrylate Bromoform (Tribromomethane) Methyl acrylate Chloroform (Trichloromethane) Methyl acrylonitrile Dibromochloromethane Methyl methacrylate Dibromomethane 44 Table 13. Reporting limits, number of samples with detectable concentrations, ranges in concentrations, and maximum contaminant levels of volatile organic compounds detected in water samples from Prairie du Chien-Jordan study area wells [pg/L, micrograms per liter; E, detection with estimated concentration] Unconfined portion of aquifer Confined portion of aquifer Number (and Number (and percent) of Range in Range in Maximum Reporting percent) of Compound samples with concentration concentration contaminant limit (|ig/L) detections in detected Otg/L) Gig/L) level (|ig/L) water samples concentrations Carbon disulfide 0.050 1 1 (44%) 0.050-E0.080 15(60%) O.050-E0.050 None Methyl chloride .200 11(44%) O.200-E0.070 9 (36%) 0.200-E0.060 None 1 ,2,4-Trimethylbenzene .200 4(16%) O.050-0.160 8 (32%) O.050-E0.060 None Bromoform .200 6 (24%) O.200-0.130 4(16%) 0.200-E0.010 '100 Chloroform .050 4 (16%) O.050-0.120 3 (12%) O.050-E0.030 '100 Chlorobenzene .050 3 (12%) O.050-E0.003 2 (8%) O.050-E0.002 100 Methylene chloride .100 1 (4%) 0.100-E0.020 3 (12%) 0.100-E0.020 5.0 Trichlorofluoromethane .100 2 (8%) O.100-E0.010 1 (4%) O.100-E0.010 None Tetrachloroethene .050 2 (8%) <0.050-E0.004 1 (4%) O.050-E0.003 5.0 Dichlorodifluoromethane .200 3 (12%) 0.200-E0.440 0 0.200 None Methyl iodide .050 0 0.050 2 (8%) O.050-E0.020 None Acetone 5.00 1 (4%) <5.00-E0.400 1 (4%) <5.00-E0.500 None Methyl ethyl ketone 5.00 1 (4%) <5.00-E0.200 1 (4%) <5.00-E0.200 None Benzene .050 1 (4%) O.050-E0.020 1 (4%) O.050-E0.020 5.0 Trichloroethene .050 1 (4%) 0.050-0.180 0 O.050 5.0 Chloroethane .100 1 (4%) 0.100-E0.060 0 O.I 00 None Bromodichloromethane .100 1 (4%) O.I 00-0.200 0 O.I 00 '100 Dibromochloromethane .100 1 (4%) O.I 00-0.3 10 0 O.I 00 '100 /j-Isopropyltoluene .050 1 (4%) 0.050-E0.002 0 O.050 None 1,1,1 -Trichloroethane .050 0 O.050 1 (4%) O.050-E0.004 200 Toluene .050 0 0.050 1 (4%) O.050-0.920 1,000 tert-Buty\ methyl ether .100 0 0.100 1 (4%) O.100-E0.010 None (MTBE) The MCL for trihalomethanes is 100 (ig/L for the sum of the concentrations of those compounds. 45 Cr U.S. GOVERNMENT PRINTING OFFICE: 1998 773-085 / 26520 Region No. 8 Water-Quality Assessment of Part of the Upper Mississippi River Basin, Minnesota and Wisconsin Ground-Water Quality in the WRIR 98-4248 Prairie du Chien-Jordan Aquifer, 1996